usb2 ports no longer work on lattepanda v1 (usb3 works)

HI, the  two USB2 ports on lattepanda v1 no longer work. the usb3 is working. In the windows control panel about peripherals I can see two roots USB concentrators the first one has a problem and the second one is ok. I've tried to uninstall and reinstall the one which has a problem : at first, it seems to be ok but after a while, the screen refreshes (in the control panel) and again a exclamation mark appears. could you help ? thanks