WordPress has been updated to 2.5.1 and the release is out now. The release fixes a very important security flaw that is said not to be public yet, but it will be. If you want to, you can nab the three files needed for this particular security fix.
The entire release have over 70 fixes, reportedly including the media uploader, which has been funky for a lot of users. As always, you should upgrade, and if you haven’t switched to the 2.5 branch yet, maybe this is the time?