I too have the same problem described by TheMarco. All of my XML headers (for feeds and for regular pages) have a leading space. For the pages, it doesn’t seem to bother the browsers, but for feeds, it’s another story.
Where is this extra space coming from? It appears on regular site pages as well as on the admin dashboard, and so it’s not specific to the theme files.
I am running version 2.0. Is this fixed in 2.0.2, or can I selectively apply a patch to correct the problem without going through the upgrade right away?