Don't get a connect with Messenger 6.1 under WinXP Prof....

Hello NG!
Now i upgraded from Messenger 4.7 witch has run realy uncomplecated under
WinXP Prof. (with all updates and patches) to Mesenger 6.1.

I don't get a connect to the messenger service behind NAT router and a
firewall (Norton 2002) but with Messenger 4.7 it worked.

Error Message is: "it seems to be a Problem with your Internet-connection
Failure 0x81000306"

In NAT router port 1863 is enabled and in Norton Firewall Messenger 6.1 has
a permit-state.

Does anyone know a solution?
Thank you!