After working fine for a long time I get no connection to the K8200 (Win7). Yesterday, when I’m heating the printer manual I lost the connection. When I connect the printer with the usb cable the two LEDs (green an red) go on. Windows says The settings for the device can not be determined Unknown Device and I’m geting code 43. When I connect the power supply the LEDs go out.
I tried the typical solutuion:
use a other usb cable
downloaded and isntalled the divers, startet the device-manager, connected the computer with the usb-cable - but ther’s no action… no usb-serial-device… 
I also checkt it with another pc - no action as well…
I allready use drivers vom FTDI for an usb-serial-converter - so i deinstalled them, installed again the one for k8200 und reconnected the 8200 - no action again…
What can I do??