I've learned my lesson! Do not, absolutely do not upgrade computers or software without lots of research, and certainly not in the middle of projects.
We were looking at my Drobo, which is a huge meaty hard drive. It was running off an ordinary USB cable. and my IT thought, it has a FW 800, why not use that, it should be better and much faster.
Oh disaster, Final Cut Pro kept crashing, spinning pizza wheel of death. Nothing would open. iCloud crap kept popping up. We couldn't figure it out. So I just shut down the computer and disconnected the 800 cable and put back in the USB back on and Voila, everything back to normal.
Well not quite. I had upgraded to Yosemite and now I can't open Compressor, Motion or Soundtrack Pro. Crap. How do I export my finished 30 GB film to a place where I can burn DVD's now?
So be forwarded, just because it is shiny and new, DON'T UPGRADE! check it out thoroughly first.