Here's a VI that I created for a project, it uses the NI IMAQ USB library, I've used a Logitech QuickCam IM with this and it works. I think the problem in your original implementation was the "USB Camera Name" input might not have been right, this VI selects the name from a list.
http://forums.lavag.org/index.php?act=attach&type=post&id=6012