hey,
some general information:
An USB Host (your machine) is limited to 500mA per host-prt (notebooks normaly have one or two host controller with one or two usb-ports)
When you now connect the U46MK2 to one host and like a mous (round 100mA) to the same controller the bus has not enough power to run both systems.
So you have to check those errors

some controller give you information that the port is full powered and not working with more devices (expensive systems) but the most controller are not the expensive controllers so they don't give you any information

So if you want to run more devices with more power you have to use an active USB hub to get enough power for all devices on the bus

.
regards
Christian