Webcam problem can get it to run

Hi thanks for looking but my dad has got a problem with his webcam ,1st off he had a cheap and nasty one fit for the job pluged it in works fine, so he decided to upgrade to a better one logitech quickcam he is also useing msn the new version ,the cammrea after about 20 seconds it starts to freeze and stick and sometimes all you would see would be a grey screen or advertisements, we checked the firewall just in case ,changed usb ports just in case ,the whole pc has had a good format since as well , i checked online for any known issues with that webcam and there was quite a few others haveing the same problem ,so he took it back and they replaced it with a microsoft vx1000 i think it is ,yet again after unstalling the previos webcam and installed the new one still got the same problems grey screen very sticky and sometimes all you see is a photo ,microphone stops working ,i ran out of ideas now so maybe someone can help on this issue?
the pc spec is
dual core 3ghz black edition amd
3ghz ddr2 8500
80 gig hard drive
hipper 550 psu
asus motherboard
xp pro + sp2

now at the moment acording to the line test of the vroadband as he is haveing some troulble with the service it is only at 1mb broadband at the moment, but the ols webcam worked fine befor,i wouldnt have thought it would have used a whole 1mb bandwith but im not sure on webcams ant got a clue
there are no conflicts in device manager
firewall is off at the moment <testing>
we have also installed the program from the disk
and have also treid the updated driver from the manfuactor no luck though

the only thing i could think of is the old speedtouch modem from virgin he is useing maybe that has got some kind of firewall in that <nat> they are seding a updated one out very soon but it is just strange that 2 bran new webcams have failed to work ,
so if anyone can think of somethink what i could have missed eather during installation or just a a gen setting any advice would be great ..

i tried to uninstall msn and reinstall it and also tried to install an older edition of msn but it keeps buging me to get a updated version and wont start ,can anyone also recomend another similer programs to use like this?
thanks for looking