Doh! Found this in the logs from my i7-3960X

[Tue Feb 10 16:36:23 2015]
Iteration: 6934673/15990667, Possible error: round off (0.4375) > 0.40
Continuing from last save file.
[Tue Feb 10 17:00:31 2015]
Disregard last error. Result is reproducible and thus not a hardware problem.
For added safety, redoing iteration using a slower, more reliable method.
Continuing from last save file.

I still say there is something wonky with the AVX code. I only have crashes on the AVX enabled systems and all of them are running stock speeds. I could accept one or two systems but 4 of 7 systems is a lot. I have non AVX systems that are overclocked and no issues at all. Only one of the systems affected is running linux. The others are running windows 7 x64.