i have a strange behavior with OS X. When I try to kill/restart my Finder with the Terminal Command "killall Finder" I get no error Message but the Finder will not restart and does not quit. Nothing happened.
With another User on this Mac everything work as aspected and this user can kill/restart the Finder.
I repaired the permissions etc..
Try using the Safe Mode.
Shut down the computer and then power it back up. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart. For each disable/delete, you will need to restart if you don't do them all at once.