Officially that board only support up to 1066Mhz. It will take 1333Mhz RAM, but you would have to overclock the RAM.
Again, officially, the board should take up to 8Gb RAM as well, but looking at the RAM support list I see no 4Gb sticks from any manufacturer listed at all.
It is possible you have incompatible RAM. I have had several cases of these G41 boards that did not like 4Gb sticks, no matter what I did.