From bleepingcomputer.com
Malwarebytes released an update today for its component package that fixes the problem with Windows 7 stations freezing. The problem was manifesting on systems with the Web Protection feature enabled in the security solution.
The troublesome installation caused the mouse, keyboard, and screen to become unresponsive from time to time on Windows 7 running on multi-core systems. The only way to get out of the lock was to reset the computer by holding down the power button.