I had the same problem. heres how to solve it.
1. Click Start, Type Device Manager.
2.Once there open where it says Universal Serial Bus Contolers all the way at the bottom of the list.
3.Another list will open, Right click in the ones that say " Usb Root Hub" there should be about 4 of them, then uninstall them all. Don't worry your computer will install them again after you restart it. Also if you have any that say "Unknow Device under the same list uninstall them too so that next time u restart your computer it will be able to identify them.
4.Close device manager after you finish with the previous steps.
When your computer starts again it will take a few seconds to install the Usb Root Hubs, then try using your cam again and it will work, It worked for me.
I hope everything goes well , if not here's my email if you need more detailed steps or any other questions firstname.lastname@example.org Good Luck!