Alt not working???

I have problem with Photoshop cs's keyboard shortcuts. Actually with just one but it's still annoying. Suddenly hotkey(s) for Step Backward function doesn't work (Ctrl+Alt+Z) anymore and don't know what do about it. I tried change the key combination but my Alt button doesen't seem to want to cooperate with me (Don't think it's a keyboard malfunction). Finally I had to use new combination excluding that Alt. Help for getting Alt back working would be greatly appreciated!!!

Thank you!

I think this type of thing usually effects certain pirated versions of photoshop...

Deker, With all respect dueI don't think it is nice to come so fast to such conclusions... Indeed, some pirated version suffer from a problem with shortcuts, so does perfectly legal ones, when the keyboard drivers needs to be updated, so mentionning that in your post implies less things, no?

So, Mad Max, the alt key works in other programs? Is it just that peculiar shortcut that refused to work? Were you working with the default KYS file, or did you load another one?
What are the shortcuts for step forward in history, or undo?

Sometimes, instant messaging programs are known to be "stealing" shortcuts. It might be another path to explore.

For those who suspect that my copy of software isn't quite legit. Indeed it is.
There was no problems whatsoever in several months. This came up just recently.
Just the Step Backward shortcut gives hard time. Both Step Forward and Undo don't use Alt-key. In Other tool like Healing Brush require use of Alt-key and then it works perfectly.

I don't think how it could be any instant messaging program, cuz when I discovered this thing, none was running.

The keyboard driver also should be up to date. Unless it expires and go bad like two weeks old milk ;)

Is it possible that I could have disabled or alter the function of Alt-key? Even though I don't recall that I'd changed any settings (I was sober :D ).

I didn't come to any conclusions, I just said that many of the pirated versions, especially the ones released right after CS came out, had some of the CTRL and ALT keys disabled and other strange things happen. People have asked that question several times on this board before, and that was the case, so it's not like I'm just calling the guy a thief.