It has been working fine for years up until yesterday... as of today I do CMD/Shift/4 and nothing happens. Nothing at all. I'm on OS 10.6.8, all four of the keyboard shortcut options are ticked in the Screenshots box in Keyboard/Preferences, I've tried logging in as a new user with a test account I created, same problem. I have been having a few keyboard issues lately (it's starting to get a bit sticky), however, the CMD key works fine independently, as does the SHIFT key and the number 4. I've been doing lots of google searches on the subject, and just can't find an answer to this inexplicable and sudden mystery. Can anyone help please? I find it virtually impossible to work without this function... Thanks in advance!