I had this problem. I was working in the previous model to the first unibody macbook pro. 15”. The computer freeze at “loading compressor support.” So first thing I tried was to plug my external hard drive to a newer mac (macbook pro 13” i7) and FCPX (also known as iMovie pro) finally finished the loading but as soon as I tried to open the project I was working on the program crashed and had to force to quit and start again. Back to my old macbook pro I tried clearing my preferences as suggested in this post and launch FCPX again for the first time it had opened since the problem first appear (and my file got corrupted). But I got the same issue as soon as I selected the project it crashed. But after several crashes I came up with the idea (I don’t know why) of dragging the project to my computers hard drive and it made a copy try to run the program again and there was no recovery file so I copy that file and un-plugged the external hard drive again (where all my files are). This time the project loaded ass offline clips but it didn’t crash as quick as alway. I managed to select it and export a XML.
It’s not the greatest solution, all the on FCPX adjustments are lost but I have the clips layout and just have to re-check every thing now. Again…not great but it was the only way for me for not starting from 0 again.
I hope this helps somebody the way some posts have helped me in the past.
Let’s hope next FinalCut it’s actually an upgrade.