Computer Freezes up after screen saver activates

Hi, I just installed the Firewall program and Comodo Antivirus is that is causing the error, so I’m certain my problem can be resolved with a reconfiguration of the system.

Whenever I leave my computer long enough for my screen saver to activate, the Firewall locks up my system and I can’t get back to my main screen. I need to reboot the entire computer. I run XP Home
with SP2.

I don’t think it has anything to do with the programs I’m running because it doesn’t matter what I’m doing at the time, other than let the screen saver activate.