Hi, Thanks so much for your response back! I checked the system preferences, and the keyboard modifier keys are correct. the Comman key is set to command.
I do not have any remapping software installed that I know of. I'm not sure what remapping software is, so I doubt it. I haven't changed or installed anything new on my computer since this started happening.
When I press Command - Shift - 3, it takes a screen shot, and puts it on my desktop. When I go to Preview and select File > New from clipboard is greyed out. It won't let me select it. I tried Command-shift-control-3 also, and nothing happened. It didn't put the screen shot on my desktop and it still didn't let me select New from clipboard in Preview.
Donald - I have tried shutting down and restarting multiple times. Didn't help.