Great blog post by Jonathan Barner:
"ISA 2006 Enterprise Edition* keeps its configuration in a CSS, which is often on a different machine than the ISA Server. In order to deal with cases where connectivity to the CSS is lost, ISA keeps relevant parts of its configuration in a local cache. This cache is stored in the registry. Whenever configuration changes are made, they are stored in the CSS, and then the ISA Configuration Agent (codenamed "Mixer") updates the local cache.
While the cache is generally well-maintained, there are rare cases where it gets out of sync with the configuration on the CSS. This can cause many problems - for example, if the cache contains an orphaned Web listener, any new listener would generate an IP conflict..."
For the rest of the story and a fix, head on over to the ISA/TMG Firewall Team blog over at:
Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer