I have the exact same problem:
http://img.skitch.com/20090722-dx1g3j1ksai92qcwqung3bfyk5.jpg
Looks perfectly normal on the index page, but goes like this on pretty much everything else (single.php, archive.php..)
Anyone with any idea what’s going on? I only noticed this today.
And it’s not a problem with my theme, I’ve tested multiple themes and the problem persists.
I’ve also just upgraded to WordPress 2.8.2, still there.