We have a Vista Ultimate pc in a SBS 2003 network. We have the TrendMicro Client Server Messaging Security solution, which runs ok on most XP pc's and another Vista pc.
Once the client part is installed, it will show the "connected to server" icon, but it can get the updates from the server. After a manual "Update Now!", it will show the "Downloading settings..." mask and then a message box will say "The Client/Agent Security Agent was unable to download updated components. there may be a problem with the network. Please check your network connection..."
Funny thing is, on the Security Dashboard, the pc does NOT show up and seems to be impossible to add.