Joe,

You nailed it. It is a paypal issue. I can't believe people were complaining about this back in 2007 and now it's happening again.

If you wouldn't mind, please post your solution to solve this via code or send me an email with your fix. I'm on my on version of the 2.3.5.4 release because I had to get the site up and running asap.

On a different note, I just want to say Thank you! You really have built a great product and I can't believe it's free. You code exactly as I would code (well maybe a little better than I would code it) so it was pretty easy for me to dive in and start making changes as needed. You blow DotNetNuke out of the water in terms of performance and I love how everything you need is pretty much already included without downloading and installing a ton of modules.

I've built 2 sites. My company website and my product website in the span of about a week and a half. Pretty impressive I think.

http://www.ntunedev.com/
http://www.lazy-admin.com/

We will be releasing our product to the new Zune marketplace for windows phone sometime today or tomorrow. If you're interested and you have a new windows phone 7, let me know and I'll give you a free license key.

Thanks,

Scott

I am having a similar problem, although it is not parameters being posted twice.  I tried developing my own membership system using the "Subscribe" button hosted by PayPal and the code samples provided by Joe.  Everything seemed to be fine on the PayPal side, but when PayPal redirected back to my site, the PDTHandler page just sat there doing nothing (white page).  I figured I was doing something wrong in code that I couldn't figure out (I have a deadline to get this site done), so I purchased the Site Membership Pro.  Installation went perfect....  I set up my test membership product, and went through the purchase process.  EXACT same thing as with my own code!

This is the url that was showing in my browser (with my test membership product):  mysite.com/Services/PayPalPDTHandler.aspx?tx=5RH12952HH858031W&st=Completed&amt=0.01&cc=USD&cm=ef258316-77f8-4f91-b4c3-e1155563d71e&item_number=

MojoPortal Version: 2.3.9.3 MSSQL
Operating System: Microsoft Windows NT 6.1.7601 Service Pack 1
ASP.NET Info: Running in Partial Trust
Server Time Zone: Central Standard Time
Server Local Time: (GMT -6) 12/28/2012 7:07:19 AM
Greenwich Mean Time: (GMT/UTC)12/28/2012 1:07:19 PM

sts-SiteMembership: 1.0.0.7

I have gone over and over the code to try and see what was going on, but I have absolutely no clue.  I have no idea what PayPal is supposed to be sending to the PDTHandler, and trying to find info on their site is painful.  Any ideas, guys?
 

My system log has never shown anything other than entries like this:

2012-12-28 07:14:38,084 INFO 2012-12-28 07:14:38,115 INFO 2012-12-28 07:14:38,115 INFO 2012-12-28 07:14:38,225 INFO 2012-12-28 07:14:43,475 INFO 2012-12-28 07:14:55,538 INFO 2012-12-28 07:14:55,632 INFO 2012-12-28 07:14:55,679 INFO 2012-12-28 07:14:55,679 INFO 2012-12-28 07:14:55,679 INFO 2012-12-28 07:14:55,694 INFO 2012-12-28 07:14:55,694 INFO 2012-12-28 07:14:55,694 INFO 2012-12-28 07:14:55,710 INFO 2012-12-28 07:14:55,710 INFO 2012-12-28 07:14:55,725 INFO 2012-12-28 07:14:55,725 INFO 2012-12-28 07:14:55,725 INFO 2012-12-28 07:14:55,960 INFO 2012-12-28 07:14:56,069 INFO 2012-12-28 07:14:59,288 INFO 2012-12-28 07:15:08,304 INFO 2012-12-28 07:15:08,304 INFO 2012-12-28 07:15:58,837

I am not working with recurring payments with Site Membership Pro.

The table mp_PayPalLog has entries for every single transaction that I attempted, so the PDTHandler is successfully writing to the database.  

There are 3 config files located in the '/Setup/ProviderConfig/paypalpdthandlers' folder: 000_placeholder.config, sts-memberpro-paypalpdthandler.config, and webstorepaypalpdthandler.config.

mp_PayPalLog shows that Provider used was the WebStorePayPalHandler.

Here is the entry for the SerializedObject column:

<?xml version="1.0" encoding="utf-16"?>

<Cart>

   <CartGuid>16f85999-7536-4c5e-bf77-b041717e3750</CartGuid>

  <StoreGuid>db83de6e-6ac6-43a7-b62f-32328e7f23d5</StoreGuid>

  <ClerkGuid>00000000-0000-0000-0000-000000000000</ClerkGuid>

  <CartOffers>

    <CartOffer>

      <ItemGuid>908a79d0-d167-44a6-8838-8b404e5a1e3c</ItemGuid>

      <CartGuid>16f85999-7536-4c5e-bf77-b041717e3750</CartGuid>

      <OfferGuid>cd6a4364-c78f-4a0c-a2ae-5f1d7a1c5423</OfferGuid>

      <TaxClassGuid>6d9569a6-614a-4da9-bb41-e2abd7144742</TaxClassGuid>

      <OfferPrice>0.0100</OfferPrice>

      <Tax>0.0000</Tax>

      <AddedToCart>2012-12-28T01:18:28.323</AddedToCart>

      <Quantity>1</Quantity>

      <IsDonation>false</IsDonation>

    </CartOffer>

  </CartOffers>

  <SerializedCartOffers> &lt;ArrayOfAnyType&gt; &lt;anyType xmlns:q1="http://www.w3.org/2001/XMLSchema" d2p1:type="q1:string" xmlns:d2p1="http://www.w3.org/2001/XMLSchema-instance"&gt; &amp;lt;CartOffer&amp;gt; &amp;lt;ItemGuid&amp;gt;908a79d0-d167-44a6-8838-8b404e5a1e3c&amp;lt;/ItemGuid&amp;gt; &amp;lt;CartGuid&amp;gt;16f85999-7536-4c5e-bf77-b041717e3750&amp;lt;/CartGuid&amp;gt; &amp;lt;OfferGuid&amp;gt;cd6a4364-c78f-4a0c-a2ae-5f1d7a1c5423&amp;lt;/OfferGuid&amp;gt; &amp;lt;TaxClassGuid&amp;gt;6d9569a6-614a-4da9-bb41-e2abd7144742&amp;lt;/TaxClassGuid&amp;gt; &amp;lt;OfferPrice&amp;gt;0.0100&amp;lt;/OfferPrice&amp;gt; &amp;lt;Tax&amp;gt;0.0000&amp;lt;/Tax&amp;gt; &amp;lt;AddedToCart&amp;gt;2012-12-28T01:18:28.323&amp;lt;/AddedToCart&amp;gt; &amp;lt;Quantity&amp;gt;1&amp;lt;/Quantity&amp;gt; &amp;lt;IsDonation&amp;gt;false&amp;lt;/IsDonation&amp;gt; &amp;lt;/CartOffer&amp;gt;&lt;/anyType&gt; &lt;/ArrayOfAnyType&gt;</SerializedCartOffers> 

  <UserGuid>8389160e-1edb-4dbd-a39e-57774582acf3</UserGuid>

  <SubTotal>0.0100</SubTotal>

  <ShippingTotal>0.0000</ShippingTotal>

  <TaxTotal>0.0000</TaxTotal>

  <Discount>0.0000</Discount>

  <OrderTotal>0.0100</OrderTotal>

  <Created>2012-12-28T01:18:28.247</Created> 

  <CreatedFromIP>68.98.29.78</CreatedFromIP>

  <LastModified>2012-12-28T01:18:28.48</LastModified>

  <LastUserActivity>2012-12-28T01:18:28.247</LastUserActivity>

  <DiscountCodesCsv /> <CustomData />

</Cart>

So, it looks like the issue does not reside with the PDTHandler, but with the '/WebStore/OrderDetail.aspx' page, since I assume that is where the PDT handler is supposed to redirect.  Right?

Using your configuration link, I solved the log4net issue.  However, in the table 'mp_PayPalLog', the rawresponse column is blank for all transactions.  If there should be rows using the site membership provider, then it looks as if those two attempts never posted anything to the database.

As stated before, here are my installation details:

MojoPortal Version: 2.3.9.3 MSSQL
Operating System: Microsoft Windows NT 6.1.7601 Service Pack 1
ASP.NET Info: Running in Partial Trust
Server Time Zone: Central Standard Time
Server Local Time: (GMT -6) 12/28/2012 7:07:19 AM
Greenwich Mean Time: (GMT/UTC)12/28/2012 1:07:19 PM

Before I try another sample transaction, I noticed something interesting.  I saw some info messages appearing in the system log.  I decided to look at the tasks queue and I found this:

Task Queue History

  Task Name Queued Started Last Update Completed Progress
     WebTaskManager 12/28/2012 7:28 AM 12/28/2012 7:28 AM 12/28/2012 8:11 AM 1/1/0001 12:00 AM 50%
     WebTaskManager 12/28/2012 7:23 AM 12/28/2012 7:23 AM 12/28/2012 7:28 AM 12/28/2012 7:28 AM 100%
     Site Membership Management Task 12/28/2012 4:40 AM 12/28/2012 8:06 AM 12/28/2012 8:07 AM 1/1/0001 12:00 AM 50%

There are two running tasks that are only 50% complete.  One of these is for Site Membership Management.  1. What task is this? and 2. Can I safely delete/abandon it before running a test membership purchase?

Okay, so here are the results of the System Log after running another test transaction:

System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 23.63.210.234:443
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)
   --- End of inner exception stack trace ---
   at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
   at System.Net.HttpWebRequest.GetRequestStream()
   at mojoPortal.Business.WebHelpers.PaymentGateway.PayPalStandardPaymentGateway.ValidateIPN()
   at mojoPortal.Web.Services.PayPalIPNHandler.Verify(String ipnForm)
   at mojoPortal.Web.Services.PayPalIPNHandler.HandleRequest()
2012-12-28 09:47:13,362 ERROR mojoPortal.Web.Services.PayPalPDTHandler - System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 23.63.210.234:443
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception)
   --- End of inner exception stack trace ---
   at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
   at System.Net.HttpWebRequest.GetRequestStream()
   at mojoPortal.Business.WebHelpers.PaymentGateway.PayPalStandardPaymentGateway.ValidatePDT()
   at mojoPortal.Web.Services.PayPalPDTHandler.Verify(String transactionId)
   at mojoPortal.Web.Services.PayPalPDTHandler.HandleRequest() 

It's not a problem on my end.  Looks like PayPal server isn't responding.