Voice and Video failure

Hi,

I have Windows Messenger 4.7, XP Pro, a DLink 613P router,
and XPs built in firewall OFF, all connected through an
Alcatel 1000 DSL modem.

I can chat but cannot have voice or video with anyone,
anyplace. It tries then tells me that either A. a firewall
is not allowing OR a Server is not allowing.

I CAN have voice between between this computer and my
laptop (XP Home, Messenger 4.7) as long as we are both on
my network (either wireless or wired) so I assume that it
is a firewall problem. I am also asking Dlink a similar
question:

From MS's point of view: What do I need to do to open the
firewall so that I can have voice with Messenger??? Ports?
ideas?? ANYTHING???

Thanks,

DOug