I have same issue but a very old mobo.
Its a ASUS K8v-MX. initially it had 256mb Hynix DDR 333MHz RAM.
Now I got 1GB Crucial @ 333MHz at eBay for re.700/- (used but description said it was at excellent condition) but it won't boot with the new ram in. after many tries i got to the windows xp loading and was seeing the system properties window. sudddenly a black screen, no HDD activity.
Restarted. again same . after that black screen immediately after power on. removed new ram and put in old one(256MB), it worked.
Crucial memory finder says :Guranteed- Compatible"
I sent the eBay seller a message and no reply...Tries bios update to latest version, clear RAM gold contats with eraser, reset cmos, pull out battery