Hi -
Hotfixes, such as security patches, can be applied to the Unity server and coincide with those applied to Exchange servers. The caveat is service packs, which typically require 60-day delay following Microsoft release until approved by Cisco, for either the Exchange OR Unity server. In the example of Exchange 2003 SP2, once that was approved for Unity, we coordinated the install for both servers, so that Exchange System Manager would get updated on Unity. If you have a test lab, like we do, with Exchange and Unity integrated, we test all hotfixes and service packs before applying in production. I research all hotfixes though, just to ensure it won't impact Unity functionality. For example, you would not want to install an Office hotfix on the Unity server because a DLL might get loaded that could impact the MAPI functionality. If the hotfix is for software that doesn't already run on the Unity server, I don't install it. In your case, it sounds like the file does exist on the Unity server. Hotfixes can be downloaded from either Cisco's site or directly from Microsoft.
Regards, Ginger