Comodo firewall v5.0.163652.1142

Hello, for a few days now after my PC has been running for a while, Comodo firewall with defence + starts to run at 50 to 70% of processor power, it goes on for many hours and will not stop until PC is turned off or process halted in task manager.
It seems to be completely up to date and there does not seem to be any other faults.
This obviously affects performance
Has anyone any ideas why, or how to stop it ? if not it looks like it will have to be replaced
Thanks, Steve Jackson