scouse,
AS I said, Zone Alarm is having a problem with Avast or if you want to look at it the other way....Avast is having a problem with Zone Alarm.
Until the problem is fixed by the Avast Team, I recommend that you change firewalls, (or antivirus).
Sygate and Agnitum Outpost are fine programs and free.
Don't ask to me to recommend an antivirus since I don't think you will find better than Avast for the price and support, but you can temporarily install AVG Free....
I know that ZA worked with the older version of Avast but the 4.5 seems to have trouble working with it.
If you have the older version of Avast, uninstall 4.5 and put back 4.1 for now.
That's all I can recommend at this time.
Sorry. :'(