WordPress keeps losing the post styling.
When you apply a style to a page, WP will honour if for a while, but after a few page refreshes it will no longer apply the style.
Then you have to go back to the page edit screen and reapply it.
Seems to be a 3.0 thing but I have no time to test that right now. It happens in the Twenty Ten theme on a virgin install, no other plugins. Not sure if it happens when I use the control panel or update the page. Haven't tested it with posts.
That's kind of useless of me, I know, but if someone else has the same problem you'll know there's something to it. And if not -- well, PEBKAC.