I've had a DVI KVM setup working for several months, using a DVI KVM and DVI Detective to switch between 2 Windows XP systems.
Just upgraded to Win 7 on one system, and now Win 7 is reporting it doesn't recognize USB devices (keyboard & mouse) that are connected.
I've reset the DVI detective and reset the switch with no luck. The Win 7 message is that its attempts to install USB drivers fails.
In the control panel, it is showing the DVI KVM switch as a unrecognised device with error: Windows has stopped this device because it has reported problems. (Code 43)
This answer would be too late for jebork but might help others in the future. I've the same problem today. I solve it by installing usb hub (it's Micro Innovations USB hub). Windows 7 installs driver from the hub then bravo!, my Gefen DVI KVM USB also works.