Should you find your keyboard shortcuts no longer working or are just plain missing, this keyboard shortcut should come in handy:
"If you need a quick and dirty way to restore your preferences, here's a way you can do it using a keyboard shortcut on launch:
Windows - CTRL-SHIFT-ALT immediately after you double-click the PS icon.
Macintosh - CMD-SHIFT-OPTION immediately after you double-click the PS icon."
Found at: http://forums.adobe.com/message/4209421