On two test sites, an update to WordPress 3.2.1 broke a theme, including the Weaver 2.0 theme which is based directly on 2010.
On the latter, I first found the front page rearranged to match one of the lay-outs on 2011. Then the Theme Admin panel broke & became unusable.
I've had no problems with the Weaver theme before.
The good news re the Weaver 2.0 theme is that I had backed up all settings, and this restored the theme to its original lay-out and widget placement, etc. (The update had lost some of my widgets as well.) The theme admin panel seems to be working again as well.
But a core update shouldn't do this kind of damage, even temporarily.
(On another site, I got a "fatal error" in switching to a different theme, but can't be totally sure it's the fault of the update.)
Glad I didn't upgrade my main site. I'll wait till all the bugs are killed!