I've recently upgraded to WP 2.5, and everything went smoothly, except that the Kubrick theme uses the wrong background for the blog, though I think it's because of WordPress.
On the main page (http://andreasaronsson.com) it uses kubrickbgwide.jpg instead of kubrickbg-ltr.jpg, which means it's completely white instead of using a tone of gray for the sidebar.
I've located the variables it checks at line 17 in header.php, in the default Kubrick 1.6 theme.
if ( !empty($withcomments) && !is_single() ) {
When this is true, it uses a background where the sidebar is gray. So it would seem something is wrong, as I only get the single-post background, all the time... :/
I've tried upgrading my blog twice, on different systems, and I end up with the same problem both times. With and without plugins.
? :(