I just built a very similar system but with 2 sticks of ram,
Q9550, Asus P5Q-E, RAM is the Corsair TWIN2X4096-8500C5DF.
I experienced random crashes, Bad CRCs, etc.
I did not do a full run of memtest86+, But there were no errors for the time I ran it,
And it passed the vista memory test...