One way mic on messenger

Using Windows live messenger and web cams with built in mics I can see my
friend but cannnot hear him. He can see me and hear me. I have checked his
control panel to make sure that his mic is working and recognised and it is
and is reinforced by the fact that using Skype we can chat but even though I
can see him he cannot see me. So to sum up using Messenger he can see and
hear me but I can see him but not hear him. Using Skype we can hear each
other and I can see him but he cannot see me but with my other Skype contacts
I have no problems both ways. Ideas please?
Thanks