I add that our device is not supplied from USB.
The solutions tested and didn't work are:
- Verifying that "Allow PC to turn off this device" in power management is unchecked.
- updating the bios
IMHO there could be several points causing this. For example, it might be a difference of USB host controllers between the working/non-working PCs. This can result in timing problems. However, this is just one of many assumptions. Another thing might be electromagnetical influence on the USB lines, etc.
1) Have you checked the USB lines with a scope on both working and non-working PCs?
2) Are the devices connected directly to the PC in both cases or is there a hub in between? Try the other case vice versa (with a powered USB hub).