I just upgraded from 2.5 to 2.5.1, and everything seemed ok when I logged into the dashboard, but as soon as I clicked the "Write" like to post a new message, I noticed some problems.
The most noticeable problem is that the "Save" and "Publish" buttons in the write sidebar blink continuously from a dimmed colour to normal colour. And the other problem is that at the bottom of the Safari window where it says "Loading... completed x of x items", the second number just keeps climbing while the first number keeps trying to catch up. I waited a while to see if the page would eventually fully load, but after the second number got up to 1500, I killed the window and tried writing my post in Camino (which worked fine).
I tried clearing my cache in Safari to see if that had anything to do with it, but no joy.