Pressing button "Deny" freezes my computer

Comodo version
XP Pro SP2
Login: as user and sometimes as admin
Antivirus now: McAfee
Firewall was: Kerio
After Comodo had been installed AVS Kaspersky was replaced with McAfee.

1 When some application (WinWord, Explorer, cpil.exe…) are trying to connect to some IP addresses and I press button “Deny” on popup window (e.g. “c\windows\explore.exe has tried to use firefox.exe through OLE automation…”)my internet browser (firefox) takes 99% of CPU. The only way to fix it is to restart Firefox.
2 If I using IE7 and trying cpil.exe there are no any alerts. But as soon as I start Firefox alerts caused by cpil.exe begin to pop up one after another.