Photoshop CS5 problem - HELP PLEASE!!

You might try resetting the Photoshop settings. Resetting often clears up strange problems like the one you are having. To do the reset, as soon as PS starts, press the Shift Ctrl Alt keys together and answer Yes.

You might want to see if anyone else here has a better idea before doing this but I've done it several times and it really isn't difficult to reestablish your preferences after doing a reset.

Hope this helps.

Kurt