Can't Pass IBT maximum w/ >1 stick ram

with the rig below, I can't pass IBT maximum or very high settings if I use more than 1 stick of ram... I tried lowering some of the settings and i still can't pass.... Not sure what else to do. I tried testing the ram individually and in separate slots and it's fine as long as I only use one. Also when using dual or tri-chanel, Games and windows don't crash.... I just can't pass IBT. any ideas? I was hoping it was just a bad stick of ram...

I ran prime95 for 12 hours and also IBT @ high settings (2gb ram usage) and I get no errors.

Instead of using IBT, try running LinX w/ >1 stick installed. It may just be IBT that's the problem, and not your DRAM configuraton.

Tech suppport told me they did some testing. and I did a bunch of testing on my own and just cant pass IBT @ high or max settings... They said not to worry about it.
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Dear Sir,

Thank you for contacting ASRock.

Sorry for the late reply.
We've done several cross-tests here, and the results are as below,

With different sockets (LGA775/LGA1366/LGA1156/AM3+ ) and different Brands MB, we found out that while "Stress Level" is "Maximum", set "Threads" as 3.4.6.8, the IBT would always failed. There may be some issue with IBT.
Since you've done several tests and the results were good, you system may be stable, please don't be worried about it.

Thank you for your feedback and have a nice day.