I have just upgraded my site form 2.3.6.7 to the latest (2.3.8.5) and now cannot get into the site administration menu.  It's running on Windows, SQL Server 2008 R2

The upgrade seemed to work fine, I reapplied my changes to web.config, and the site is up and running, but when I try to get into the administration menu I get an error page:

Any ideas?  Other site design pages seem to be working

I can see the following error in the log:

'mojoPortal.Web.Commerce.PaymentGatewayManager' threw an exception---> System.IO.FileNotFoundException: 

The full asp.net error is:

   System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) +9718543
   System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath) +1142
   System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize) +81
   System.Xml.XmlDownloadManager.GetStream(Uri uri, ICredentials credentials, IWebProxy proxy, RequestCachePolicy cachePolicy) +77
   System.Xml.XmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn) +69
   System.Xml.XmlTextReaderImpl.OpenUrlDelegate(Object xmlResolver) +75
   System.Threading.CompressedStack.runTryCode(Object userData) +70
   System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) +0
   System.Threading.CompressedStack.Run(CompressedStack compressedStack, ContextCallback callback, Object state) +92
   System.Xml.XmlTextReaderImpl.OpenUrl() +191
   System.Xml.XmlTextReaderImpl.Read() +207
   System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace) +114
   System.Xml.XmlDocument.Load(XmlReader reader) +114
   System.Xml.XmlDocument.Load(String filename) +128
   mojoPortal.Web.Commerce.PaymentGatewayConfiguration.GetConfig() +376
   mojoPortal.Web.Commerce.PaymentGatewayManager.Initialize() +26
   mojoPortal.Web.Commerce.PaymentGatewayManager..cctor() +40

[TypeInitializationException: The type initializer for 'mojoPortal.Web.Commerce.PaymentGatewayManager' threw an exception.]
   mojoPortal.Web.Commerce.PaymentGatewayManager.get_Providers() +0
   mojoPortal.Web.CommerceConfiguration..ctor(SiteSettings siteSettings) +334
   mojoPortal.Web.SiteUtils.GetCommerceConfig() +383
   mojoPortal.Web.AdminUI.AdminMenuPage.LoadSettings() +92
   mojoPortal.Web.AdminUI.AdminMenuPage.Page_Load(Object sender, EventArgs e) +13
   System.Web.UI.Control.OnLoad(EventArgs e) +91
   mojoPortal.Web.mojoBasePage.OnLoad(EventArgs e) +14
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

Sounds like you are either missing the mojoPaymentGateway.config file in the root of the site or else you have a web.config/user.config setting pointing it to a custom file that is missing

Hope that helps,

Joe