Hello DanF and forum users, HAPPY NEW NEAR!.I think I have a problem that is close to yours, but I tested my ram with memtest86 for 6 hours without any error(all at once, not piece by piece).My system was bought 3 weeks ago, and I installed the system 3 times, I have random blue screens.I took the sytem to warranty, but they said that the system worked perfectly and they did not had any problems.They tested the system with PC CHECK.

My system is:

CPU TypeQuadCore Intel Core i5-2500K, 3300 MHz (33 x 100)
MOTHERBOARD NameAsus P8Z68-V Pro
Memory Module Name 4 X Kingston 9905403-171.A00LF
Latest bios for my motherboard BIOS Version 1101
Hard Disk SAMSUNG HD502HJ SATA Device
2 optical drives HL-DT-ST DVDRAM GH22NS50 ATA Device (LG) , TSSTcorp CDDVDW SH-S223Q ATA Device (SAMSUNG)
One Corsair 850W power supply.
One COOLER Master computer case.

and my latest DUMP file error read with blue screen viewer is:

DUMP FILE: 123111-24320-01.dmp
CRASH TIME: 12/31/2011 4:48:21 AM
BUG CHECK STRING: MEMORY_MANAGEMENT
BUG CHECK CODE: 0x0000001a
PARAMETER 1: 00000000`00041287
PARAMETER 2: 00000000`00000030
PARAMETER 3: 00000000`00000000
PARAMETER 4: 00000000`00000000
CAUSED by DRIVER: ntoskrnl.exe
CAUSED by ADRESS: ntoskrnl.exe+7cc40
FILE DESCRIPTION: NT Kernel & System
PRODUCT NAME: Microsoft® Windows® Operating System

Please help! I really want to solve my problem, because I am a video editor, and now I stay with my projects unresolved.I tested the HDD, but I don't have any bad sectors.When I installed the first windows 7 on this system 3 weeks agod, I had another problem, a blue screen caused by USB 3.0.I connected 3 logitech webcams to try a podcast.2 webcams connected to usb2.0 ports and 1 to usb3.0.When I connected the logitech c510 camera to usb 3.0 blue screen appeared.I entered to the motherboard site and updated the usb 3.0 firmware and after that I did not had problems with the usb 3.0.After I resolved that blue screen problem I had other blue screens with this type of error that I posted.Another problem is that my monitor searches the video CARD (onboard cpu) and sometimes cannot find it, searches analog/digital and then black screen remains.(does not enter to w7)Now I want to escape from this blue screen, and then I will buy a dedicated video card, because the onboard video card has issues.Thank you in advance for your help!