Ballistix modules are usually non-standard in their voltage requirements. Most (if not all) of the Ballistix DDR2 modules on Newegg show a 2.0v requirement (vice the 1.8v standard); and the DDR3 modules all show 1.65v (vice the 1.5v standard).
I've seen a couple of cases where simply replacing a pair of Ballistix modules with a pair of standard voltage modules resolved very perplexing intermitten memory failures such as what you've described.
What is the make/model of the motherboard? Also, what is shown for the voltage on CPU-Z (look on the SPD tab and select the modules one-at-a-time). http://www.cpuid.com/softwares/cpu-z/versions-history.html
... Note that the make/model of the motherboard will be shown on the "Mainboard" tab of CPU-Z