Theres some out there ( tools ) that are decent at working the crap out of a MM and catching it failing. But Im at a loss for remembering one thats available right now.
Some software test will only be marginal for stress testing a RAM module. Thats why in most cases, performing swaptronics is cheaper back-water way of trouble shooting.
I use a hardware diagnostic device called R.S.T. 
and my revision  is quite old already.
Their website is here, http://www.uxd.com/memory-diagnostics.shtml
I suggest anyone with unexplainable gobblins and phantoms and a few extra bucks invest in stress tests of all memory.
Bus memory, physical memory, video memory (BFG ) , Freeking disk memory, theres a lot of stuff to test outside the physical RAM modules too. This company makes quite a few products for testing just about anything.

-But please do get a full error message when possible, write it all down except for repeating hex.

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