The service Microsoft Firewall does not start on ISA 2006 computer. You get the following error:

Cannot load an application filter Web Proxy Filter ({4CB7513E-220E-4C20-815A-B67BAA295FF4}). FilterInit failed with code 0x80092004. To attempt to activate this application filter again, stop and restart the Firewall service.

The problem could be problem with the certificate in a weblistener

Source

http://www.active.se/active/kunskaper/isa/