vendetta-1.8.312 Crashes on Ubuntu 14.04 (trusty) GNOME 3.8.4 Kernel 3.13.0-40-generic. Screen freezes on game startup after login requiring a hard reboot. Repeted a couple of times.

It shouldn't require a hard reboot unless your video drivers locked up. Try Ctrl+Alt+F2 then log in at the console and type pkill vendetta. You should be able to switch back using a different key liek F1 or F6

OR switch desktops if your enabled multiple destops on your system with CRTL+W then go to dashboard and type system monitor which is the taskmanager equiv.

Then you can kill vendetta with the clickety method if you like