"It will show up under Usb devices as an Unknown Device.. sometimes.
I gave up after about a year of frustration.. (ice) cold booting worked.. completely power down, remove the plug from the wall, wait a few, don't plug in anything but the keyboard/monitor/power and try to login, if it fails, shutdown/restart again. Try all the USB ports, make sure its a full-power USB2 port if possible. If necessary, uninstall all USB ports/devices then shutdown.
It still works beautifully in BIOS/DOS/linux/my laptops/LiveCD's.. just not the work box's XP.. odd. Stupid dell.. so much easier to blame you than Das!
Some slight googling suggests replacing the mobo battery might help.. don't see how, but anything would be worth a shot, I know how great that kb is! Some more ideas here: http://www.compatdbdotorg/support/topics/176233_usb_device_not_recognized_malfunction,8.html Which is a phenomenally long thread, full of people suffering the same thing with a multitude of devices.. and all the varied ways they have attacked the problem.. its not just Das.. apparently it could be the chipset itself, which rebooting resets, and resistalling mobo drivers might be the ticket.. (haven't tested yet)"