This sounds like you are probably using the old CANDASH cable which also has serial wires inside, this will interrupt PC comms when connected.  The CANDASH cable was originally designed for our old DisplayLink dash which used both serial & CAN depending on what ecu it was connected to so is not ideal for a for a CAN only dash.  The quickstart guide we package with the dash suggests the connection is made with a CANF connector which wouldnt give you this problem. The solution is to cut t