Is the image window active? Click anywhere in the window before using Ctrl m. Or use a Curves adjustment layer.
yes the image is active, gueest I'm goin to stay with the curves layer adjustment, thanks a lot Trevor
Not that the keystroke shouldn't work for you, and not that a Curves layer is a bad idea, but have you considered invoking the functionality you want to use via the menus (e.g., Image - Adjust - Curves)?
I would try Noel's method, to get to Curves, and when finished, check to see if something else on your computer (did not know about the Bing bar, but could be any number of programs, that use hot-keys) has not "hooked" Ctrl-M.
I had a screen-cap program, that loaded part of it, at bootup, and it hooked about 1/4 of my PS hot-keys. Maybe check out what is in your MSCONFIG (if you are on Windows), in the Service and Startup Tabs - anythiing there, that uses hot-keys?