Replacement memory won't boot!

[Tooks]

Got a strange problem here. I was running four 512mb sticks of identical Corsair Value 667 DDR2. One of the kits developed errors verified by memtest, and was RMA'd.

I then continued running my system on 1 of the kits, whilst I waited for the replacement kit.

I received these yesterday, and installed them in my system, and with them installed it just won't boot! Remove the sticks and everything is fine again! I installed the RAM after returning my system to stock OC wise.

I've checked the specs, and they appear identical to the faulty ones. Even with the faulty sticks installed, my PC always booted.

With just the replacement sticks in, it still refuses to boot. I wonder if Corsair have changed their specs in the last 6 months?

Any ideas on the best way to diagnose this?

 

[Tooks]

Computers are strange beasts sometimes...

I was all set to order a 2GB set of decent memory because of the above problem, (2GB really helps my photoediting/gaming etc), but in a fit of madness only reserved for people fiddling with computers, and in an effort to avoid spending another £150 on my PC, I thought I'd try installing the new RAM one last time.

What do you know, it works just fine now. I've turned off and re-booted several times, and everythings ok.

Oh well, I shouldn't complain, but I wish I knew what was happening!