DDR400 problems (adding new memory)

I've tried adding a ddr400 512mb stick to my existing 512mb.

I have a soltek sl-kt600-rl board, which supports ddr400 up to 3gb with three slots.

When I first added the extra 512, it registered at the POST screen, but when logging into windows my system just rebooted. I have tried swapping the modules around all over the place, but that didn't help. Now My system wont boot with the second module in at all.

Both modules are functional, the one I added running in another system, the first one running in my system right now.

They are different manufacturers, my original is a TwinMOS DDR400 CL2.5, and the second one I tried to add is Hynix DDR400 CL3. I noticed the different CL ratings and set CL in my BIOS manually to 3 as well as setting the frequency to 400MHz, but that didn't help.

Does this sound like standard compatibility issues? What's my best bet for getting a module to run with my TwinMOS? The Hynix is my brother's and I was just "testing it", I'm wanting to buy an extra module for myself see.

P.S. there is a setting in my BIOS called SDRAM interleave, would this have any bearing on the problem?

Should have said so, but I tried clearing the CMOS with jumper, didn't actually remove the battery but it did reset the CMOS.

After that is when it stopped booting with the second module at all.

I have updated my BIOS to the latest already, and had tried putting CAS up to 3.

Will try the voltage thing, what's the likelyhood that that much overvoltage could do damage?

Your motherboard isn't compatible with that companies ram? It happens.