I honestly think it's caused by the excessive compound. We shall see. 
The one I cleaned is still running, no zombies.You might have seriosly cracked this case wide open mate. Its nearly 24 hours and by now I have to be resetting something... still going well
250MHz @ 800mV = ~62.5Gh/s - Stable!
Looks like I need to follow suit. Thanks irobb and ppumpkin for identifying this.