Offer Remote Assistance through Windows FireWall

Environemnt:
- Windows XP Pro with SP2 on both nodes.
- Remote Assistance & Remote Desktop Enabled on both nodes via system remote
tab.
- Offer Remote Assistance enabled on both via gpedit and added users for the
helpers.
- Windows FireWall is activated on both nodes with both Remote Assistance &
Remote Desktop enabled in the exceptions.

Problem:
When attempting to offer remote assistance I get error "The Remote server
machine does not exist or is not available". When I turn off Windows
FireWall, I'm able to offer Remote Assistance just fine.

Question:
What do I need to do in order to Offer Remote Assistance with Windows
FireWall enabled. What else do I have to do besides what is already enabled
and active as listed above?

Thanks for any help