Can't talk

My brother and I have no problem having file transfer,
video and audio on MSN. Both our systems are running on
XP. I have McAfee Firewall.

2 weeks ago, my brother installed a Linksys router to his
machine. After that, we can only have file transfer and
video, but audio is not functioning. Somebody told me
that a program called 'Real Tunnel' will solve the audio
problem. Have you heard of it? Does it work?

How can I fix the audio problem? Thanks