OCZ ram upgrade problem

I have been running Q9550 at 430x8.5=3655Mhz + 2x2GB OCZ2P10664GK ram at 400Mhz 5-5-5-18-54-2T for a few years stable.

However with the same settings, now that I added another 2x2GB of the same ram for total of 4x2GB, I get instant black-screens (shutdowns without bluescreens). I ran memtest86 and got about 8 failures in 1hr at 430x8.5, and about 2 failures in 1hr at 400x8.5. However, the black-screens still happen regularily in Games at lower clock speed 400x8.5, regularily means my system turns black within 30min in starcraft2. But so far no black-screens when under normal win7 environment running photoshops.

anyone with experiences on 4 sticks ram upgrade? some directions on improving stability in games would be appreciated. ( I'm sure the sc2 bnet ladder players would greatly appreciate it too)