So what do you think is the problem? (2.4c OC)

[aggressor]

Just got done doing Extended tests on the sticks, 1 at a time. Both passed with no errors @ 220mhz. They fail at 215mhz and higher when both are in, in dual chan mode.

What does this mean?

 

[stardust]

dual channel is more vigorous on ur memory, thats why dual channel kits are sold. Their SPD timings are altered to help ease things up.
lowering CAS latency would help, consult CPUZ for stable timings.

 

[aggressor]

Well, hopefully the Corsair 3500XMS I bought will be better. They don't sell those in dual channel configs though :\

 

[stardust]

no need they're top of the line