ram timings changed and now no boot

ok so i recently changed the timings for the ram on my motherboard as they are guaranteed to support 1066mhz, after the pc rebooted i was greeted with just a black screen and no monitor signal, my keboard lights are not on and my hd4870 displays 3 lights that mean internal core temperature fail, and external power a/b are unplugged (they are not)

any idea on what the problem is? i have less than 18 days to find the fault and RMA the failed parts, i am very tempted to just take it into a shop and get them to find it as it would be a hell of a lot easier! I am going to do a CMOS reset, do you think this will fix it? if not do you think the mobo has died on me? I checked the psu using some equipment and it appears to be working fine, all fans are moving and the mobo has a green light!

thanks <3

ok cmos worked, now i just have to fix my tf2 crashes