Tried that -- didn't help. I wonder if a re-install of the OS would help -or- it that a bit more trouble?

I am a new Mac user (LOVE my new iMac) --- but I have a strange problem. The left "command" key does not work the same as the right "command" key. The left one just causes the screen background to darken, wereas the right one I can do the normal copy, paste etc. I did take the keyboard into the ...