Comodo preventing Windows login

Hi. Just installed Comodo after reding the good reviews. But now I cannot login to my pc. If I set Comodo to disabled (I have to do this in safe mode) all works fine. As soon as I increase the protection - even to learning mode - it stops me logging in. I am using XP Pro. Any ideas?

Did you run a scan with Comodo? DId you happen to block something that should have been aloud? Go to the D+ tab/Advanced/Computer Security Policy and see what you blocked.