As it turns out, there wasn't anything wrong with any of my cards. As I added cards to the MB, booted up and tested I never swapped out the video cable so that it always is attached to the card that would be "GPU 0"
If the monitor is not attached to the first card on the board it always goes sick...but if the monitor is attached to the first card everything works perfectly. I now have 4 cards on the MB mining at 610+ kh/s with no issues.
If this is something that is obvious to others then I apologize for my ignorance...While I've built many systems before (and some with dual GPUs) I've always attached monitors to both cards and I've never really used them for this type of activity (mining) so I didn't realize that there was any importance to where the monitor should be attached.
Thanks for the responses.
Also, grue, I would agree with you as so many often point out that Intensity 20 is pretty darn high, but in this case I didn't think it was a root cause because I've been mining on all these cards (on two separate MBs) using Intensity 20 for weeks...so that couldn't be it.
As for the clock speeds being so low, yes they were...but my attempts to change the settings were being ignored by the card....
Anyway, so at least in this case the solution was just to attach the monitor to the first card (GPU 0)
PERFECT - I had the same exact issue as you and plugging in my monitor the the CPU0 & it FIXED My Sick - DEAD GPU. Ughhhh took me too long to find this post to figure it out...
I must have re-configed every possible setting before I found this post.
Thanks for writing up your fix!