Have (or did) you another Anti-Virus installed in this system, if so what was it and how did you get rid of it ?
What other security based software do you have installed. anti-spyware, firewall, etc. ?
Can you still move the mouse pointer whilst the screen is frozen ?
Yes, I can move the mouse
I installed Malwarebytes' and Comodo firewall
Some have experienced a problem with avast5 and MBAM paid version with resident protection conflicting ?
Whilst I don't know why this an issue, some have disabled the resident function in MBAM and that has resolved the problem for them, try that first.
Comodo current editions aren't stand alone firewall but CIS, which includes multiple modules including an anti-virus and this could also be the problem if the CIS AV is installed ?
So if you have the CIS AV module installed you can and should use the add remove programs to remove it.