MOBO and RAM help please

[NewbieBuilder]

Hi

im on a new build and i have Abit AV8 Mobo and if you can imagine the 4 Ram slots

like this

1 2 3 4

each number representing a ram slot

Ive got 4 x Corsair 512mb DDR 400 RAM
this is the problem
i can put ram into banks 3 and 4 and the system works
if i put ram into 1 and 2 the stystem starts but doesnt boot.

if i put the same RAM from 3 and 4 which works into 1 and 2 then the system doesnt boot.

is this a setting error stopping it from working or is the Mobo faulty?

Thankyou

*edit* with the speaker connected i got one long Beep on startup