If you receive an answer from PMDG, could you post the answer on here? I'm having similar problems using the 737NGX as I can be flying along great and then certain key commands freeze up and I'm stuck with the view I have. I have a lot of add-ons I use too, and as long as its not the 737NGX, I can run the recommended 30 fps all day. And of course I set my system up as recommended by PMDG three times, one time a whole new, fresh installation of FSX as recommended by PMDG.
Thanks a lot