Quadro 4000 issues w/ PP CC. Crashes MacPro during rendering and exporting in Encoder.

Question

I'm using a Mac Pro 3,1 early 2008 w/ 2x2.8 GHz Quad-Core Intel Xeon w/16 GB RAM, Nvidia Quadro 4000 is installed and the factory installed NVidia GeForce 8800 GT for dual monitors. I also have a Blackmagic Design Deckling HD Extreme installed but mainly only use it for the XLR audio outputs to my Mackie Mixer. I'm running Yosemite 10.10.2 and all drivers have been updated.
I finally made the switch to PP CC from CS6 thinking it would make my life easier, boy was I wrong. What a mess. Playback in the timeline is laggy and it seems like the audio is just a bit behind even though technically it is in sync. Makes it very difficult for precise cutting to a quick beat. Main problem though is when I go to Export the Media. As soon as the progress reached a spot in the sequence that I know was not fully rendered in the timeline, the display flashed and then froze the MacPro. I had to manually shutdown. Then I tried to render all the clips still with the yellow bar so that the entire sequence was green. I had to do it in small increments because if I tried to render more than about 10 seconds of the sequence the same crash occurred. Once the entire sequence had the green render bar I tried to Export again. Sure enough, once in Encoder the processing starts out normal, but then as the export continues the processing starts to slow down and then came to a crawl, literally 5 minutes to process perhaps one 5 second clip until it got about halfway and bang, the same flashes and weird pixelation patterns on my displays and then the MacPro  froze. Again I had to do manual shutdown and then start back up. After struggling with this till 3 in the morning I did notice that at some point when I reopened Premiere I got the following missing render error msg. "This project was last used with Mercury Playback Engine GPU Acceleration (Open CL), which is not available on this system. Mercury Playback Engine GPU Acceleration (Cuda) will be used." Ok, so something tells me there is an issue with my NVidia Quadro 4000 and Premiere CC.
If anyone has figured out a solution please let me know. Right now I just can't afford to buy a new Mac so I'm hoping perhaps a simple solution or even purchasing a different acceleration card to replace the Quadro 4000 will do the trick.

Answer 1

Yes, latest version of Yosemite, all drivers are up to date. All fans working. I have always used 2x 23" Apple Cinema displays, but they are using the GEForce8800 Graphics card that came with the Mac Pro in the other PCI slot. So the Quadro 4000 is not connected to any displays. Internal Media RAID is 3TB with 2.4 TB still available. I did not keep any settings from old CS6 version of Premiere. Here's an update for you. Its the Quadro 4000 for sure. I talked to PNY, the manufacturer, and they said to pull it out of the Mac and see if the problem goes away. So I did, and of course the problem went away. I also tried installing it in different PCI slots, but to no avail.  I also bought a brand new 3TB internal Seagate drive and I did a clean install of latest Yosemite and all the necessary drivers for the Quadro 4000 and installed Premiere CC on it. I had the exact same issues when running PP CC on the new internal drive. So that pretty much tells that its most likely a defective Quadro 4000. Unless you can think of something else that I am overlooking.