Turns out my freq was just a bit high. I dialed it back to 800 from 820 and my U3 has be running splendidly along with my other devices with cgminer on Windows. Sorry that MacMiner didn't work out, but so it goes!
FYI, I have since given up on MacMiner and grabbed a cheap laptop to run cgminer in windows. Works perfectly fine here. Although I had a moment where it dropped down to 20 GH/s. I unplugged it for a bit, relocated it closer to a fan, and restarted c…