Mac (OS X 10.9.2) no longer saving screen shots
When I try to take a screen shot (Command + Control + Shift + 4) 


That's the problem. The shortcut to put a screenshot on the desktop is just Command + Shift + 4 (or 3).  Don't press the control key; when you do, it copies to the clipboard instead.  That's why you're not getting a file on the desktop.