Uh oh, so you're working on some super l33t code or other stuff that is super important and Linux Mint's MATE or Cinnamon window manager freezes. This means maybe you can move your mouse but you can't click anything, you can't Alt + Tab to another program but everything appears to be working other than that.
The first thing you would do is Ctrl + Alt + F1 (or whatever virtual terminal you want) and get into the Linux bash prompt (the black screen where things really happen :))........
If Linux Mint 17 or other has no window buttons/controls you can do the following from terminal:
marco --replace&
Sometimes it can be fixed if you go to your themes/appearance and choose a new one but in the case like mine where Compiz is installed but not running/working then that fix will not work and will require the marco command above.
What if you can't type in a terminal Window?
If you close........