I had the same issue with OA and Avast. Neither program is to blame, but both are to blame, if you can follow the logic.
OA has HIPS and when Avast starts, OA will allow it if you have given permission. When Avast updates, then because both security programs try to start first, OA sees a change in AVast and will block it until you allow it, HOWEVER, windows hasn't started to the point that it will allow OA to notify you, hence the computer stops.
You can update Avast, then tell OA to go into training or learning mode while you reboot, or go into Avast and tell it to load last. Either way, it should allow OA to see the updated Avast and then ask you if it is kosher.
I'm not sure if Comodo has the same issue as it didn't choke when I had it installed, but I know that OA does. However, that is why my brief stint with a HIPS FW is over. I do not have the patience to fuss with all this security BS and have gone back to basic security, such as a FW that is just a FW and, so far, an AV that is just an AV.
Just my enormous knowledge at work
Colin