dlinear:
I disagree.
You claim usbser.sys is the culprit.
Nothing here...
MSP430 with the same issue: MSP430USB versus FTDI - MSP low-power microcontroller forum - MSP low-power microcontrollers - TI E2E support forums
...applies because you are not pulling out the USB cable.
This appears to have no relation to your problem...
Hacked version of the driver for low-speed transfers: http://www.recursion.jp/avrcdc/lowbulk.html
Which leaves this...
Noise induced on the USB data lines causing a bug in usbser.sys to become problematic. Less noise = fewer problems. More shielding = less noise. Better cable = more shielding. Better cable = fewer problems.
I have tried numerous types of cables from various vendors. This does not seem to make a difference.
Which indicates you are buying cables from the wrong vendors, that you have misdiagnosed the problem, or that you have an incredible electrical noise problem.
If your project is affected by the usbser.sys bug then a shorter better USB cable will help.