is your system powered from a socket with grounding?
I've had some systems in the past that were acting like that when powered from a socket without grounding.
Wouldn't unplugging the UPS to force use of the battery remove any possibility of there being an issue with the wall outlet? I'm going to check the outlet with a ground tester anyways. The only other thing I can think of is maybe the built-in wifi card causing some kind of EMI interference? I notice they give you an antenna with long cables in the box, but I've been using my own antennas that are only about 2 inches long.
Both the LAN ports ? That's a bummer...Is Gigabyte working on it?
I use wireless, so I disabled both. I opened a ticket with tech support and got the same questions, did you try this and that. Found this thread and asked the question and someone answered with the solution. You may try disabling one at a time and see if it works. Good luck.