MSN Messenger (av) behind NAT / router

Hi,
my router's supposed to support UPnP however I'm having problems setting up audio and video in MSN Messenger (instant messaging is ok).
I'm running XP Pro (SP 2) and a ZyXel ADSL router.
Firewall security set on router only (no software firewalls on the computers)
DHCP active.
I have a successful audio connection when using Skype but cannot access audio or video on messenger. Some sites have recommended opening TCP ports 5004 to 65535 for video (TCP/UDP 6901 for voice) since the UPnP doesn't seem to be working. Isn't this a huge security risk? Any ideas??
Another part of the problem may be NAT - do I need to configure static IP addresses?

 

some progress

Hi,
just to update - I discovered that UPnP was in fact turned off on the router - so that has been corrected. I've also opened TCP port 1863 for MSN Messenger. So far have I've managed to get video without sound (Europe to Australia - from snow to sun!).
I think MSN Messenger runs VoIP which is probably creating problems with the NAT in the router. Having searched as much and as long as I have time for I've opted for using MSN Messenger for video and Skype for audio (Skype runs on P2P technology and has excellent audio).

I'm also looking into Netmeeting - if anyone out there has any problems with Netmeeting, routers etc.... I came across a comprehensive article dealing with that (includes port numbers, security etc).

comprehensive info on Netmeeting
http://www.meetingbywire.com/Firewalls.htm

 

update on NAT problem

Still seeking a solution - so far my searches have turned up two articles that seem to suggest that it's not possible to have audio and video on MSN Messenger when the computer is behind a NAT router.
Microsoft suggests setting up a proxy server (not a route I want to go down) in the following article.....
MSN Messenger Service Cannot Perform File Transfers or Make Voice Connections Through NAT
http://support.microsoft.com/?kbid=278887

and from MSN Messenger ...
http://messenger.msn.com/Help/Issues.aspx which seems to suggest that a UPnP NAT device should allow audio connections. There's a reference to turning off the QoS Packet Scheduler Bandwidth Limiting if you are using XP and an Intel Internet card (which I am)
Does anyone know whether turning it off will affect wireless networking or anything else I might need?

Seem to have similar problems with iChat on my MAC.

any help would be very appreciated - thanks