Shift + T not working on Apple Wireless Keyboard
I did that once by accidentally setting an application hot key to be Shift-(and some letter key). Did you recently change hot key settings? If not, did you install something recently that may have had hot keys. If all else fails, try rebooting in Safe Boot Mode (hold down the Shift key on startup until the gear starts spinning), log in and see if you can type. When you are done in Safe Boot, restart w/o any keys.