Digital video isn't meant to be transferred via USB.
MiniDV camcorders: The camera of choice for the amatuer videographer, the miniDV camcorder is now a proven and mature product. The camcorder connects to a PC for capture via a Firewire (also known as ilink), which is a lossless process - what you see on your camcorder is exactly what's transferred. If you don't have a firewire socket, you can buy a PCI expansion card for about £10 from any PC retailer. Once connected, you'll be able to control the camcorder on your PC using editing software such as Pure Motion Edit Studio, and DV files are ideal for editing and supported by all editing software currently available. (Videoforums FAQ)