Responce to Dual Channel Memory problem

Check each ram module separately in each ram slot, see if pc boots.
eg. Test each module in ram slot 1 first. If only one module fails to boot that module is defective. If all modules succed to boot in slot 1 then all modules are ok. Now check the other three slots using just one module in one slot at a time. This should determin which, if any, slot is down. If all slots are ok and all ram modules are ok then you have either a compatability/timing problem or possibly a voltage/PSU problem.
Hope this helps. All the best Craig

PS better to use just two slots for dual channel performance.