Two different Timing/voltage RAM in the same system

I have been running two pairs of different memory together for maybe 6 months, they are both 1gig Corsair XMS2 DDR2 800mhz except one pair has a voltage and timing of 5-5-5-18 1.80v and the other of 4-4-4-12 2.10v .

Despite the differences these four sticks worked happily together for the past 6 months, except yesterday either nvidia's motherboard update or window's 7 update decided to break this ignorant marriage.

Now the only way my system will boot up happily is with just one set installed, I have tried both combinations for having all 4 gigs in the system, with one the system gives out a long beeeeep and hangs, with the other the system hangs on the boot memory test.

and the mother board is a
Evga 750 SLi FTW

I was digging around the bios, and couldnt really see a way of setting the memory timings/voltages differently per ram slot.


...so My question is this, is there any way to get this to work? If I roll back and use the evga motherboard drivers (and not the nvidia ones) to get it to work (assuming thats what did it) am I hurting the system?

any help would be appreciated thanks!