Thanks for getting back to me, Syd. I'm running a mid-2011 27 " iMac. Apple told me that Mt. Lion, unlike Mavericks, was not a true 64 bit program which is why FCP 7 is able run on it. Therefore, they won't guarantee me that FCP 7, 32 bits, will run on it. On the other hand, FCP X is 64 bits, so it's no problem with Mavericks.
So, if I understand you correctly, you are still working in FCP 7 on Mavericks without a problem.
May I ask did you do a "software update" over Mt. Lion or did you wipe your drive clean and install Mavericks and reinstall all your old apps? That would be a lot of work.
Final question: are you doing much work with FCP X and, if so, liking it? I took a tutorial on the trial version last spring and have to admit I wasn't too crazy about it. As a long time FCP user since 2001, it seemed like a stiff learning curve. I would love to hear your thoughts.
In any case, thanks so much for your valuable input.
Best,
Phil