I have been having the same issue as @pslettershome and since upgrading my system to a new Mac Pro a week and a half ago. I have to run with GPU acceleration off and I also noticed I cannot use dynamic linking with After Effects without freezing up the entire OS (and the AE builds are very basic). Most of my projects are setup with ProRes codecs and these crashes/freezes/heavy visual artifacts in my renders are very upsetting. Not to mention trying to figure out workarounds and constant restarts have made me miss deadlines, not good . How does one resolve this? How can I downgrade the OS and is that really necessary? Are PP 2014 users experiencing this?
My setup:
Premiere Pro 7.2.2
Mac Pro (Late 2013)
OS 10.9.4
2.7GHz 12 -Core Intel Xeon E5
64GB Ram
FirePro D700
1TB internal HD
AJA IO/4K
Pegasus 2 R6 External RAID