Cannot Start Offer Remote Assistance Session

Archived from groups: microsoft.public.windowsxp.help_and_support (More info?)

I've been battling this for over a year now trying to get Offer Remote
Assistance to work on our Domain. Everytime I try to offer remote assistance
to another computer I get the error:
"There is a problem with the invitation and it cannot be opened. To use
Remote Assistance, the sender of this invitation will have to send you a new
invitation."

Here is what we are running:
-All computer are on our domain.
-We are running a Windows 2003 SP1 environment with Windows XP SP2
workstations.
-All computer are fully updated with Windows Updates
-We do not use Windows Firewall on any machine
-We are trying this internally (external firewall is out of the question)
-Group Policy is enforced by the Servers and all workstations are forced to
update Group Policy everytime a user logs out.
-Offer Remote Assistance is enable and so is the Solicit...whatever policy.
-Administrators are part of the Helpers group.
-We do not have to DCOM policies enabled, and from what the White Page on
this sounds like you do not have to do any special configs if it is not being
used.
-I even tried updating the local GP with the offer remote assistance stuff
to see if that helped.

Anyone have any additional ideas. This would help our IS department out
alot instead of having to physically go to a users computer everytime they
have a problem. Thanks.