audio over internet has stopped working

I have not been able to start an audio conversation over the internet since
upgrading to version 6.2 of MSN
Messenger on Windows XP. Before the upgrade my contact and I could use
audio conversation without any problems. Since upgrading to 6.2 it has not
worked at all. We have tried uninstalling QoS and that did not fix the
problem. We can still send video in both directions. Audio conversations
still work between my 2 PCs on my LAN. Since the problem started the
"Connecting to" message in the status bar of the IM window takes a long time
to come up after clicking on accept for the audio conversation and there is
a long period of time that I am locked out of typing in the IM the window.
We had the same symptoms before upgrading to SP2 and upgrading to SP2 did
not change any of the symptoms.

Both systems are connected to the Internet via DSL. My system is behind
a Linksys router with UPnP enabled. None of that has change since audio was
last working. Anything else to try to fix it?

Thanks,
Rod