Messenger 6.2 Audio

For the last couple of weeks I have been trying to have
an audio conversation with a friend of mine using
messenger 6.2. My friend can hear me speaking clearly
thru the headset, but apart from a few distorted words at
the beginning of the conversation all I seem to get is a
tinny rythmic pulse and then the connection terminates
after a few moments. Instant messenger works just fine.
I cant seem to find where the fault as everything is
properly working and enabled. Ive checked my firewall
settings and messenger is allowed by both firewalls i
have installed the Microsoft security Centre and a McAfee
ive tried disabling each firewall in turn with the same
result when using audio. Can anyone help as ive
contacted messenger support and what they suggested ive
tried with no success. My friends has been able to have
an audio conversation with another friend so i think its
my computer that has the problem but unless im told that
there is a fault and where it is theres very little i can
do to fix what could be causing this.
My Computer
Windows XP Home
SP2
Messenger 6.2
1.1 MB Broadband
Creative Audigy 2
McAfee firewall Microsoft security Centre Firewall
My Friends
Windows XP Home SP2
Messenger 6.2
1.1MB Broad band
Microsoft Security centre firewall
thanks for any help or advice.