Hey dude, I think I figured it out, especially if it's an old HUI, UPDATE THE FIRM WARE!
I hope that's it.
later gator-Scott
I'll pray that this was it. Also, make sure that you have selected the HUI in the peripherals menu. Plug it in, unplug it and then open up PRo Tools and go to peripherals, and have it search using midi or ethernet, whatever it's using to talk to the other.