Phenom II X2 550 unlocked stability question

So I decided to buy a phenom II X2 550 just for the heck of it. I have been interested in the dual to quad core stories that i have been hearing about. So I gave it a shot.

System specs

Phen II X2 550BE
Gigabyte ma790x-ud4p bios F5
corsair 4gb 5-5-5-15 @ 1066mhz
hsi 4890 1gb gpu
creative X-Fi titanium fatal1ty profesional
corsair 750tx psu
2x seagate barricuda 500gb 7200.12 raid-0
Vista ultimate 64bit sp2

I got the chip popped it in and booted up into the bios. In the bios I enabled the ec firmware to hybrid and set the acc to auto. Saved bios settings and rebooted my comp. To my suprise my rig booted up registering a phenom II X4 B50 proc. Loaded windows no problems. CPU-z registered it as the phenom II X4 B50 proc as well. From there it was on to the stability testing. I ran windows experience index first and it successfully passed with a 5.9 rating. From there it was on to prime95. I ran the blend test first for some reason. I ran the blend test for 3hrs with no problems. Then I ran the FFT test for 8hrs. no problems. After that I decided to run pcmark vantage 64bit edition. Finished all tests no problems. From there i ran sisoft sandra lite 2009 edition. All tests passed with no problems. Here comes the interesting part. After running tests with no problems I figued that the cpu was stable and decided to try out some gaming. So I booted up steam and jumped into l4d. started a game and this is where i noticed some graphical problems. It seems that some frames render just fine and others not good. Then after an intensive zombie battle the game crashes back to desktop. I get no bsods and system operates fine after the crash.

Next I tried to bump the vcore voltage a bit to see if maybe that would help take care of the problem. Nominal bump of .025v. It seemed like the graphical problems actually got worse. Just lookin for suggestions as to how to get stable in games or some benches that would test for something similar to gaming. Id like to find where the instability of the system is. An help would be appreciated.

Those 2 extra cores were locked for a reason: they did not pass the tests for the chip to become an X4!!!
Lock them again, and see if your glitches are gone.
If they indeed are, then you were out of luck and the 2 extra cores are defective (that's why they where locked).