Akai S1000 / S1100 samplers

I have four 8 meg ram modules with my s-1000HD and they worked when i
bought the sampler, 

but now i can only use 4meg of it in the o.s.

I tried moving the ram modules around in different orders, but without
success.

Can someone give me some insight in finding the bad ram module(s) and
setting up the good ones? Or could it be the ram slots?



thank you,
Michael