Memory not recognized although compatible!!!

[zer]

Hi there. I just bought a 2Gb kit (2*1Gb) DDR2 800 , to replace my current 1Gb DDR2 667. Motherboard is an Abit KN9 ultra, which i checked that will be... happy with the new memory (compatible). When i install it nothing happens. No boot. Only a black screen and a periodical beeping sound.
Any help? Bios update needed (as a friend of mine suggested)?

Rest of the system:
AMD 3800+, Radeon X1900GT, a DVD writer etc
Any help please??

 

[zer]

Thanks for your answer.
Motherboard definetelly supports DDR2 800 (just rechecked it)
I re-installed old memory modules- everything runs fine!
But i didn't tried each stick by itself and i only tried the slots i previously used.(there are two other beside).
Could it be that i haven't PUSHED hard the sticks? i am kind of afraid to apply force. Are these OCZ "thick" sticks more difficult to insert?

 

[zer]

OCZ 2Gb (2*1Gb) DDR2 PC2 6400 platinum Revision 2 Dual Channel