I have notice that if I have Motion and FC 7 open, and running a lot of sequences, the performance of FC playback decreases. If I close out of Motion and close open sequences, things do not improve. If I then restart FC, playback is back to normal. My guess is something is not releasing memory.
There was a post a while back with a way to clear allocated memory, but I can't seem to fine it. Is there a way of clearing the memory without restarting the program?
The most recent OS updates seem to have several unintended "sideaffects" in the way our Macs perform when running Pro Apps. I too have found the need to reboot often as of late, with significant slowing and even kernel panics as the price of not doing so.
A complete system rebuild did nothing to eliminate the problems. And, after checking in with several other very technically competent users, it seems many, but not all, have been experiencing issues recently.
So, you might want to just continue rebooting more frequently than you're used to if indeed there is some type of issue with the OS, and pray the next update rectifies it.