what the? (memory problem)

[Teny]

okay, i know all my ram works perfectly since i ran the memtest, but whenever i put a stick in the forth slot, all i hear are long beeps and once in awhile it would just start normally. when i put any of those stick in slot 1-3, it seems to work fine, but its the 4th slot, but then again, sometimes when i restart my computer, there wont even be a post beep. i ran the memtest again and they all passed again, anybody know whats wrong? my rig is on the bottom, and i have 2 1gb and 2 512 mb, cant run dual channel since the timing is wrong, but am able to run single once in awhile, as long as i close my computer for like 5 min and turn it back on, but then i cant OC. when i run cpu-z and have all my sticks in the 4 slots (tried in every order, all i get is sometime 2 gb and sometimes 3 gb, but on cpu-z when its on 2gb the second and third are only 512, but i know one of them is 1 gb, and when its 3gb it says the 4th slot is missing one. is it the mobo or the cpu?
thanks in advance.

 

[sek3o1]

i think you need a bios update .... idt your board is able to handle the memoery some boards don't play well with others (memory) so check out there fourms and such.