Frequent lock ups of my P7N Diamond

Question

Here are my system specs:
Intel Core2 Quad Q9300 @2.50Ghz
P7N Diamond
Nvidia GeForce 9800GTX
Creative X-fi Xtreme Audio(came with board)
Hyundai Electronics Zion DDR2 800Mhz 2GB(1GBx2sticks)
Corsair CMPSU-620HX PSU (620W)
Segate Barracuda 500GB hard drive
Windows Vista 32bit
The problem is My computer restarts anywhere from 5min to 2 hours while playing a game and sometimes even while just browsing the internet and watchin videos.I ran
memtest and sticks are perfectly fine.I have the latest video drivers(185.20) and other necessary drivers are also installed.Disabled all unnecessary items in BIOS on the motherboard
like spread spectrum,eist etc and since i came to know from other threads about the video corruption issue,i updated the bios to 1.2B1 still the problem persists.the system is completely unpredictable as it simply locksup with the audio goin into an infinite loop with the video still.I hav everything running at stock speeds includin CPU,NB,DRAM all set to auto.
My memory timings are 5-5-5-18 with command rate 2T at 1.8V.CPU,system and GPU temperatures are normal.Please help me as i am not able to hav a stable system.Suggest any remedies for this issue.
thanks

Answer 1

ok i will up the CPU and NB voltages as u specified and lets hope its the end of this problem and i hav disabled the spread spectrum in the bios before only..
well as per the CPU-Z here are the list
From SPD tab
Timings table
Frequency:           200MHz           266MHz           400MHz 
CAS#Latency:        3.0                  4.0                 5.0   
RAS# to CAS#         3                    4                    5
RAS# Precharge:      3                    4                    5
tRAS:                     9                    12                  18
tRC:                      12                   16                  23
Command Rate:       2T                   2T                  2T
Voltage:                1.8V                1.8V                1.8V
And from the memory tab
Current timings:
DRAM Frequency:                 400MHz
FSB:DRAM        :                  5:6
CAS#Latency(CL):                5.0 clocks
RAS# to CAS# Delay(tRCD):   5 clocks
RAS# Precharge(tRP):           5 clocks
Cycle time(tRAS):                18 clocks
Bank Cycle Time(tRC):          23 clocks
Command(CR):                     2T
Wat is the next step??
thanks
PS:Can u tell what u voltages u hav set for the CPU and NB in ur board for now??