Try and look for a readme.txt on the webcam software cd. It might have some issues with a scanner and webcam running at the same time. If it doesnt have any thing try the webcam manufacturers site and go to a link there called support and look for some info about this issue.
Hope it helps
Murph's Law: 1.Everything takes longer than you think
2.If anything can go wrong it will
3.Nothing is as easy as it looks