rss feed from page with html?

I use WP to run a blog into a pre-existing page with html and php elements. I do not use WP themes. When I ran version 2.07 I had no problem with this and RSS feeds loaded fine in FF and other readers. I just upgraded to 2.7 and now the feeds don’t validate.

Running this url

http://wingstaiwan.com/?feed=rss

through the validator shows the problem is junk after the document element. I understand there is not supposed to be anything after the /rss tag. Somehow this used to work in 2.07, and I guess that version produced the feed in some other way, maybe one that didn’t involve grabbing everything from the index.php file.
Is there some way of doing this? I really don’t want to have to use an off-the-shelf theme for my site or write one from scratch to include the elements I have there. The blog is a small part of the content I have up.