Probably something hosed in your User Account. You could log in to a test account (create it if you don't have one) and see if it has the same problem.
If not, you could try going back into your usual account and open the Library folder (Option + Go Menu > Library) open the Preferences folder and drag out the com.apple.finder.plist file, then restart.
No, no, don't delete Preferences folder - just com.apple.finder.plist.
Finder will be set, after Mac reboot, to its default settings (like it was when first booting into new OS X).
No, no, don't delete Preferences folder - just com.apple.finder.plist.
Finder will be set, after Mac reboot, to its default settings (like it was when first booting into new OS X).
Correct!
But I'm not sure it would be a disaster if you did. Most plist files are probably factory default anyway. It will let you delete the folder, but I think a new one would be created upon Restart.