Pc wont boot if memory installed in first slot of either channel a or

[donkeywax]

recently put two installed two new case fans and now system wont boot,
this is a old problem that went away,
if i put strip of memroy in either slot a1 or b1 the system wont boot, however its fine with memory in slot a2 and b2, so ii am having to run my two sticks in two differnt channels.
i have a asus m4n75td
corsait xms3 1333mhz 2x2gb
i would like to run my memory in dual channel any ideas thankyou

 

[donkeywax]

Turned out CPU heatsink retention bracket was loose,

my ex and her boyfriend stayed for a few days and i told him about xbox360 overheat cause heatsink comes away, wasnt only surprise he left,

my advise dont let your exs new fellas in your house especially when there small minded little pricks called micheal charlton