Web cam camera

I do have a small problem with my web cam and I'm trying to get some help below is the explanation.
I have Acer(aspire onr) small PC and has camera isntalled incidenthe computer (crystal eye web cam) but I can not make that work and everytime I'm trying to use that on the MSN as you know I would like to se people and to be sen when I talk to them but that is not happening (buki does not have video and voice conversation installed (or it is disabled) and is not able to accept your invitation)this is the message that I'm gettinjg all the time.