Try logging in with another user account and see if you're having the same problem. If you don't have another user account, make one temporarily to test with.
I would try trashing the Finder's preferences file, "com.apple.finder.plist".
Your Spotlight may not have ever indexed this kind of system file, so you'll probably have to navigate to it manually. If you only have this problem with one user account, just trash that user's preference file, probably in the /Users/"YourName"/Library/Preferences folder, substituting "YourName" for your short user name.
While you're at it, trash your sidebar preferences file too, "com.apple.sidebarlists.plist"
It should be in the same folder.
If the problem appears to be system wide, try trashing any files by the same name from the system's local library folder: /System/Library/Preferences.
Keep in mind that some systems place these files in slightly different locations.
If you're on one of the later versions of OSX, these folders are typically hidden, so you'll need to navigate to them from either the Go->Go To Folder menu item or Terminal. Admin access will probably be required to trash user domain resources, and root access may be required to trash system resource files.
Once you've trashed both files, restart the Finder (or the whole computer) and see if that solved your problem. The Finder should remake these files for you, sans corruption.