You probably have a conflict with some Mac OS X system shortcuts. Go to System Preferences > Keyboard > Shortcuts.
In particular look at the Spotlight Shorcuts. I've changed them to Ctrl + Space instead of Cmd + Space. Also Ctrl + Option + Space instead of Cmd + Option + Space.
Wow, that might just be the answer! Thank you, Steve, for the speedy reply.
Even though I've been using the modifier keys for ages with the Adobe products, this issue has only been happening for about 4-6 months, and the past 1 month mulitiple times a day now. So I sure hope your suggestion does the trick from now on.
Let us know whether that works for you.
Well, I went along without a hitch for a week or so after changing the Mac OS X system shortcut for Spotlight.
But now I have the problem back again, not being able to use my Adobe shortcut keystrokes for Hand tool and Zoom tool.
Any other ideas would be extremely appreciated. Thanks!