I baught some OCZ Fatal1ty Edition memory rated at 1066 MHz (2.1v)

After installing it (motherboard supports up to 1066 without OC, 1600 OC'ed) the machine was just crap. I couldn't even start the XP installer. I "slowed" the memory to 800 by reducing the DRAM:FSB ratio and the PC running perfectly. After I finised installing everything I tried setting the BIOS back to "by SPD" settings and the machine was unusable again.

I also tried setting everything manually according to the ratings on the memory: 5-5-5-15 2.1v, but this didn't help either. I did some reading on various sites and apparently memory that is rated 1066 MHz at 2.1v is overclocked out of the factory as "normal" DDR2 memory runs at 1.8v.

Can anyone verify this, or perhaps give suggestions as to how to get the machine stable with memory running at 1066 MHz?