Unity 4.04, Exchange 2003. Two integrations, Call Manager and serial to Intecom switch.
For a site that is on CM, the MWI calls are routed to the Intecom legacy switch which then errors since the Intecom does not know about the CM extensions.
The switchID settings in the subscriber table and the switchID setting on the notificationMWI tables match. They did not match on these folks, I manually made the change to match them. The subscribers used to be on the Intecom switch, moved to another site that has CM. Both sites are on the same Unity server for voice mail.