Ok I connected my roter and HC2 to a grounded outlet, changed the ethernet cable between router and HC2 and updated my HC2 to a newer firmare and all was well. I then disconnected from the grounded wall socket to the original ungrounded socket and after two months the HC2 has not lost its connection.
I'm not sure which of these two did it but I'm very happy it works now. Hmm I think I even updated the router to a newer firmware during all this too...