Hi Selmore,
That doesn't sound like a typical problem. Usually there is no relationship between a network connection and the USB port; however, there is a possibility that they share interrupts and somehow one resource is getting confused by the loss of another.
Have you tried this on any other machines? I know that Windows XP tends to handle lost connections better than Windows 2000. Also are you using a laptop of a PC?
By trying it with a different system it might help us narrow down exactly what is occurring and why.
Regards,