For the past few days, I've been unable to undo anything using the keyboard shortcut, Ctrl+Z. Using undo via the Edit dropdown menu is still possible, though. It's just annoying having to select undo from a menu when I want to undo something quickly or in succession. The keyboard shortcut doesn't work in any of the applications -- Word, Excel and Access '07, Photoshop and Flash CS3, and Firefox -- that I've been using for the last few days. So, yeah, any help on how I can get the keyboard shortcut working again will be highly appreciated.