Quote Originally Posted by Jon. View Post
Both Ethernet and usb are digital so noise is likely to effect both if large enough, i have my uc300 running an inch away from my 2200w vfd and two inches from a honking great 55v toroidal transformer without issue so sounds like your noise may have been in your power supply, were you using ac filters? either that or there was something massively wrong happening in the next room.
I suspect Jazz's source of interference was a HF Plasma Cutter, or HF TIG welder, both of which will produce and emit interference that will far exceed anything a properly wired VFD will.
If you get the chance, you might want to try firing one up next to your machine, and see if it still remains as stable, as there's nothing quite like a few hundred volt high frequency unsheilded arc to highlight the slightest deficiency in your shielding/grounding/power filtering/communications.