Avast has some "issues" with Faronics "Deep Freeze"
You have to install deep freeze first and then install avast. If you install Deep Freeze after avast, Deep Freeze will install, lock your computer into the protected mode, and then avast will kill off the controller and icon. The net result could be the need to do a fresh install of your computer if your not careful.
or a very time consuming work around.. that only works if you did not register Deep Freeze.