I'm lookinginto this. It works correctly under windows so it seems to be a bug in mono but I'm not entirely sure yet. I will investigate this weekend.

Under mono it seems to keep items grouped together by feed rather than sorting items descending by date accross feeds. It is using a DataView object with .Sort  = PubDate DESC

I thought I had this working but it seems to have regressed for a couple of feeds. There is a bug in mono for the DateTime.ParseExact but I had a workaround that I thought had fixed these particular feeds I am thinking of in the Aggregator but they are not working at the moment so I need to look at whether I did some post fix tweaks somewhere along the way and broke it . It still displays the feeds but if it can't parse the pub date it dates them 30 days ago so you don't get old ones floating to the top but if you aggregate multiple feeds they don't sort correctly. I'll investigate further this weekend. I have this nagging vague recollection that I saw something I thought could be formatted better in the code and changed it withuot testing afterwards. I did comment out the original code when I did it so I can go back.

It doesn't like these formats:
Mon, 09 May 2005 18:38:30 EDT
Mon, 09 May 2005 14:56 -0500

It does like this:
Mon, 09 May 2005 13:48:21 GMT

I guess if all else fails I can write my own little parsing routine and convert them all to GMT format then adjust them to GMT time

I would fix it right now but I'm working toward getting this site setup on a hosted server that has much more bandwidth. My traffic has been going up and I have seen times when it seemed slow at peek traffic hours

this is fixed as of release 20050530