Upped memory frequency - memtest causes shutdown, but once only?

[Artheas]

I'm overclocking my RAM at the moment, i've 'de-stressed' the CPU, and trying to see how far the RAM will go.
I upped the memory clock to 250MHz, then booted using the memtest86 disk. Once it's fully loaded, the blue screen (of the program, not of death) appears for a split second, and then my machine shuts down.
The weird thing is, if i turn the machine back on, with the same settings, memtest then loads and runs fine.
So i did that, then upped it to 260MHz, and the same thing happens again =/

Any ideas why?

I'm using 2Gb Ballistix DDR4000, 3-3-3-8 2T

 

[Artheas]

Piece my motherboard doesnt want it at 1T lol

I'm getting a new one, more money wasted

 

[Artheas]

Abit an8-sli.

I reckon i'll lose about £30 selling it as used, and it'll cost about £150 for a new one, so thats £180 for my new mobo :''''''''(

Of course, i dont know that it is the mobo thats the problem for sure, which is why i'm thinking of getting 'the best' OC board, so that i dont have to buy new RAM to test as well.