I'm finding that System Prefs freezes and inability to log out or shut down are fairly common. One suggestion on the Apple support forums was to reboot while holding down the Option/R keys to reinstall the OS. That poster claimed that it appears to have corrected the problem.

I've repaired permissions, done fsck -f, run DW, and reset the PRAM. But I'm still getting SP freezes and blank gray screens when trying to shut down or log out. Plus I've disabled or uninstalled a few older, rarely used apps, and removed others from LogIn items.

So trying the reinstall option may be worth a shot. But will that nuke my user folder? Do I need to copy things like my Mail folder, or will that stuff be untouched?

What's weird is that my MBP is virtually a mirror of the Mini, but I have not experienced any of these issues on the laptop.