just for giggles, lets try to run just vixen (even though it's not your normal app) with the etherdongle plugin for dmx, when you run a sequence (make make up some random stuff for a quick sequence of like 10 secs) does the mag jack light flash more frequently than when the sequence stops? this is the quickest very simple way to test, then we can try to see if it's hardware, software, or network settings