First thing is Web cams suck up alot of Power and rescources...I would make sure you have a good power supply, and make sure nothing is running in the background when using the Cam.....
Also make sure you have the VIA USB Filter patch installed...>>>>>
USB 1.10 Filter Patch
And also if possible when the cam is connected try to get into the device manager and look at the Hub it is on, make sure the Voltage used is no More than 400mm to 500mm, if so then you need an external USB self powered HUB