BleepingComputer.com: Problem with system lockups on new computer

Hi everyone. I'm having troubles with lockups on this current system.

CPU: AMD Phenom II X4 955 Black Edition Quad Core
Motherboard: Gigabyte MA790XT-UD4P w/ Version 5 bios
Memory: Mushkin HP3 996629 4GB 2X2GB DDR3-1600
Video: XFX Radeon HD 4890
PS: Antec Truepower New 750W Modular Power Supply
HDD: Western Digital 7501AALS Caviar Black 750GB SATA2
DVD: Samsung SH-S223B/BEBE 22X DVD+-RW SATA

Memory settings:
Sticks running in outer slots.
Memory clock: x8.00
Timings: 8-8-8-24.
1T/2T Command Rate: 1T
DDR3 Voltage Control: +0.25
CPU NB VID: +0.1V.

It's a complete lockup. No response from the keyboard, the sound locks, video locks, and I sometimes lose my video signal. It has never once restarted on it's own, nor have I once seen the BSOD.

Sometimes when I restart the system after a lockup with the ram in the innerslots, the system completes POST fine, but will not load beyond that. I am instead confronted with a small green block and an "N" beside it in the middle of the screen and the computer halts. When this happens, I can restart, go into the bios and just select save settings without changing anything and the system will boot as normal. This hasn't happened with the ram in the outer slots.

I have already exchanged my ram once with an identical pair, thinking that I had faulty modules. The new ram runs successfully in Memtest for more than 12 hours in both the inner slots and the outer white slots. I have them slotted in the outer white slots of my mobo, as my system seems to lock up less with them there and I don't get that green block and "N" issue.

My HDD passed both a Quick and an Extended test in Data Lifeguard. My temps are all normal and fans working properly. I have all the latest drivers installed.

I'm running Windows XP Pro 32-bit... I had Win7-64bit RC installed, but reverted back to Windows XP during the first round of lockups to rule out software issues.

I'm wondering if it could be something wrong with the motherboard, or maybe a bad mobo/ram combo? Could a faulty video card cause a full system lockup?

Thank you!

Rhyan

Take out the graphic card and try without it.

Try one ram at a time.

Before doing reset ur cmos settings default.