So its treating your phone like a WWAN device like if you had mobile broadband built into the computer instead of treating it like a ethernet over usb connection. If there is a network connection showing up for it try to go in and force it to allow the phone to handle DHCP. Tethered phones act as the DHCP server in most cases, but if it thinks its an internet WWAN device the computer might be trying to be the DHCP server causing a conflict. Or force it to somehow recognize it as an ethernet connection.