Performance undeniably improved after cleaning the thermal paste. By this I mean the units lasted longer but still Zombie'd. Replacing the USB cables then let me get to where I am at today. It might be worth just changing the USB cables without doing the paste to see if that would have been enough as cleaning the paste is a pain and is not for everyone.
I never got 3 to run together because I sold one before I got the new USB cables.
Now after running for a few days one of the units will Zombie. Unplugging/replugging gets it to work again but only for a short while. Cycling power and USB plug/replug gets it to work for another 4 days or so.
Hope this helps.
I have used my own USB cables since day 1, my first U3 would not run at all with the factory cable. My second U3 I threw the factory USB cable in the trash right away.
Were you able to run two U3s together before you cleaned the thermal paste is I guess what I'm getting at. I haven't applied paste since I build my computer years ago, I know it's a pain, which is why I'm putting it off, but I just may have to try it to say I've tried everything.
Other than that maybe my computers have USB issues, I read through this thread again and noted at least 5 different people who were able to run 2 at once. I wonder why it works for them but not for me.