memtest: single channel passes, dual channel fails?

I recently built a new pc. It worked fine for a day or so. Then I started getting random crashes and BSOD's. I ran memtest and it found a bunch of errors. It found errors only in test 5 [Block move, 64 times] and test 8 [Modulo 20, ones & zeros]. So I tried switching from dual channel to single channel and memtest passed. I've left it as single channel for about a week now and have had no errors. So it was definately the dual channel causing all the errors before. I'm using crucial memory (2 identical sticks of 512mb pc3200 ddr400) which I bought brand new of course. I'm just wondering if the memory can be classed as faulty? Crucials website does not say it can be used in a dual channel configuration. So I'm thinking they'd just take it back and it'd test as fully working.

I've tried the sticks in all four of the mobo's slots. All parts of the pc are new.

Any thoughts/ideas?

Specs:
ASUS A8n-SLi Se mobo
athlon 64 3700
2x crucial 512mb pc3200 ddr400
sata II hd

Thanks for any help!

no one? :(

When you bought the memory did you buy a dual channel pack or two single sticks of 512Mb?. If you did not buy a matched pair that might be the problem or you could try running each stick individually to see if one of them is faulty.

Alternatively try a matched pair of dual channel memory if you have one\can borrow one to see if it corrects the problem.

And just double check that you are putting the sticks in the right slots as per your mobo handbook (ie) normally 1 and 3 or 2 and 4.

This might seem a silly question, but have you tested each stick invidividually?

It sounds like one stick is at fault here, so try putting in just one stick, running the test, and then try the other stick. If both pass then you have an interesting problem :) But you can try and RMA to crucial and explain , you never know what they will say.

As for buying dual channel kits etc - they are just marketing gimmiks it's mostly irrelavent. I have run memory from 2 diff manufacturers in dual channel together before without problems...

try increasing the dimm voltage a notch or two.. if that fails, try underclocking slightly (400 down to 380ish) and memtest again