The symptoms of 'not working' are as follows (and all symptoms seem to be able to occurr on a single problem computer):
-Sometimes when the device is connected, Windows says "Device Not Recognized" (code 43).
-Sometimes when the device is connected, windows does identify the device, but shortly thereafter it says it is not working because the device cannot start (code 10).
-I have done some work with netmon and it seems that there may be 'bad config descriptors' on this problem machine.
My hunch is that this chipset is more picky in some way than others, which causes this not to work.
In terms of identifying the chipset....
We connected our device to approximately 10 computers. All of the computers that had problems with the device had Intel 5 series USB ... in the Device Manager. None of the computers that worked had this chipset listed for USB.
Also, I see that that status USBD_STATUS_CRC is returned when the bad config descriptors happens. Is this a HW problem with the chipset, maybe?