2 of 3 mem slots bad??

Everything works fine otherwise. Verified the chips are good. It only recognizes memory in one of the slots. Its 2x256 PC2100 DDC Micron. So only recognizes half of the memory or no memory depending on which slots the chips are in. Tried tons of BIOS settings to no avail. What could the problem be? Gotta be mobo right? But all other operations are fine. Board is an Epox 8KHA+.

p.s. This actually for a friend so if you need additional info I'll have to ask him.

Thanks.

UPDATE: He says slot 1 reads the memory correctly, 2 and 3 read only half.

is that with only one stick in?? because ur supposed to only one stick in the first slot. have u tried both sticks with one in the first and the other in the second slot??

--jason