A while back I mentioned an issue where an upgrade of an SMS 2003 client to Service Pack 3 will cause NetMeeting Remote Desktop Sharing to fail. Well, there's a fix available for this issue available per Knowledge Base article 941820.
You can download this fix without having to contact product support by requesting it at this site:
As noted here, there is a fix/workaround for this issue if you have run into it. You can read about the specifics of the problem in KB 941820.