I think the newer Whistlers are incompatible with many, if not most, versions of Windows 7 due to recent software and firmware changes. Basically, because the driver is unsigned and the device subclass is incorrect, Windows tries to install a USB driver to the device and lists it as "Unknown Device" under USB due to the incorrect subclass number. It's probably possible to change registries in Windows to trick Windows into thinking it is a Comm device or at least a truly "unknown device," but I'm not interested in messing up my computer for all other uses due to one poorly implemented product.
Note: What I said above does not apply to the 1040.