After upgrading from ISA Server 2000 to ISA Server 2004 this weekend, the MS Proxy/ISA provider for Avast has failed to start. Avast reports that “[t]he provider is waiting for a subsystem to start.”
There are no recent errors in Avast logs.
What can I do to fix this problem?
Ken
Hello,
is avast filter visible in the list of installed Web filters (in ISA configuration). Perhaps the installation was not migrated successfully during the update. You should then try to “Repair” the avast! installation from the Add/Remove programs panel in Control Panel.
lukor,
Thank you very much! 
You were correct. The Avast filter was not migrated to the upgraded ISA Server. I ran Avast Repair and the problem was fixed immediately.
Ken