Random BSOD no clear culprit

I'm fed up trying to find the culprit to my recent random BSOD crashes, please help. Here is a bit of history.

I'm running win 7 x64. 2500K, Asus P8Z68-V PRO, 16 GIG RAM OCZ, 7970 Vid card, Xonar STX.

I was having some random BSOD crashes late last year. Ran memtest, found errors almost immediately, isolated the bad RAM module and had it RMA.

After that comp ran great for about 3 months, suddently about 3 weeks ago I started crashing often. I figured it was another mem module, I ran memtest, nothing. I ran it overnight several times, one time even for about 20 hours, and it found nothing.

It seems like my crashes are becoming more frequent and I have no idea what it is. I haven't installed any new software nor hardware.

I'm still leaning towards bad memory, but why on Earth won't memtest give me a single error?

Included are some of minidump crashes from Nov. to today.

Thank you.

All the four BSODs of this month reports the same thing.

Code:

fffff880`0b815838  fffff880`01279a9aUnable to load image bdfwfpf.sys, Win32 error 0n2
*** WARNING: Unable to verify timestamp for bdfwfpf.sys
*** ERROR: Module load completed but symbols could not be loaded for bdfwfpf.sys
 bdfwfpf+0xca9a

That is, as your system say .....

Code:

\??\c:\program files\common files\bitdefender\bitdefender firewall\bdfwfpf.sys

Uninstall BitDefender. How to uninstall Bitdefender

Use Microsoft Security Essentials as your antivirus with windows inbuilt firewall, and free MBAM as the on demand scanner.

Download, install and update those, and then run full system scans with both of them, one by one.

Let us know the results.