OK, lets see if it's something goofed up on just you as a user. You should set up another profile if you haven't already, go to System Preferences, Accounts, and on the left click the + sign to set up another user, call it Test Account or something. Once it is set up then click on the Apple in the upper left of your screen and log out and then log then log into the new account to see if you are still having a problem. If the problem is gone in the new account then you know it's something with your account and not the computer. If it still isn't working OK then do a PRAM reset:
http://support.apple.com/kb/HT1379
If you still have problems time to get on the phone to Apple, the number is in your owners manual.
Roger