The motherboard is a Gigabyte GA-8SR533 and it has two USB controllers and root hubs. OK that gives me different interrupts and memory ranges, but I don't see why that would be a problem?

The only difference that I can see is that when the Maxell is attached to the pair that boots normally it is consuming 80mA but in the one that hangs it is 100mA. It is supposed to support 500mA per device.

Weird, but not a real problem.

The only reason I mentioned it is that I know people use these drives for diagnostic software and the like, and that some have been set up as boot devices.................... that wouldn't work in this situation, and if you tried a reboot after using the drive it wouldn't work, which would be confusing.