Rob Gutermuth wrote: “I’m running the last OS that will run [FCP7] on a Mac Pro 5,1”
There are OS that will run FCP7, and there are OS that will run FCP7 well. We here have a volume with OSX Lion that runs FCP7 well on our Mac Pro 5,1. FCP7 has no problem at all with ProRes HQ clips 1920×1080 60p resident on good quality HDDs with eSATA connection.
It’s hard to get FCP7 to run well. The system settings, etc. take some fiddling. It’s naïve to expect FCP7 to run as well after an OS upgrade. When ours didn’t, we reinstalled it, helped by Jon Chappell’s nice Preference Manager. But it still didn’t work as well as on Lion, so we returned to Lion. Certainly try reinstalling FCP7 on whatever OS you’re running, but if this doesn’t resolve your trouble consider setting up a volume with an OS on which you knew it worked well. The greatest pleasure of the Mac is the ease of multiple bootable volumes. Perhaps the greatest displeasure is the ease of OS upgrades which can come with firmware upgrades which can spoil earlier OS volumes.