I have noticed on one of my blogs, since I updated to WP3 once in awhile it will keep telling me there is an update available (has the "1" next to the updates link in the admin menu), but when I click on it there are no updates available and the "1" goes away. The next day I will see the "1" again.
If there really are updates (say 2), it will say 3 until I click on it and then it will say 2 and show the 2.
Would could be causing this? I am stumped myself and haven't been able to solve it via trouble shooting.