Computer details:
Core2Duo E6750 3.2GHZ(8x400), GigaByte GA-P31-S3L, Corsair 2x1G DDR2 PC6400 C4 @ 1:1RAM (5 5 5 18 @ 800),
Themaltake Armor Jr (Aluminium Modded), Nvidia GeForce 7300 (512MB), 160G SATA W/Digital HDD,
CPU Scythe Ninja (120mm Fan), FANS: 1x120mm Front, 1x120mm Rear, 2x120mm Top Exhaust

I'm been overclocking this Mainboard (GA-P31-S3L) now for about 6 months, and altho I can get it Orthos stable for countless hours,
I'm getting irregular cold boot issues. Meaning the board reverts to stock settings, and I have to go back in and restore my overclock.
I've tried every combination of voltage increase, FSB speed, and always tried to keep a 1:1 setting. Even with Ram set to Auto,
I get this problem. At the moment, I can only seem to hold a 3.2Ghz o/clock (400x8) with Vcore 1.328v in Cpu-Z.
I've added +.1v to PCI-E, +.2v to FSB, and +.2v to MCH.
The ram timings are manually set 5 5 5 18 @ 2.1v, with 1:1, so running at 800Mhz.
Any FSB above 400 tends to bring out the cold boot issue real quick. I believe the Ram is verified to run at 4 4 4 12 @ 400Mhz,
but as soon as I tighten the timings, altho it runs stable, it won't cold boot regularly.
I've researched my motherboard, and am confident the P31 is a reasonably good overclocking board,
and as I'm not overclocking the Ram, I'm curious as to why I have the cold boot issue.
I would be more than happy to get a stable 3.6Ghz o/clock.
If anyone has any ideas on memory timings etc, I'd greatly appreciate it.
Sorry for the long read.

Below is a Everest Overclock report:

--------[ Overclock ]---------------------------------------------------------------------------------------------------

CPU Properties:
CPU Type DualCore Intel Core 2 Duo E6750
CPU Alias Conroe
CPU Stepping G0
Engineering Sample No
CPUID CPU Name Intel(R) Core(TM)2 Duo CPU E6750 @ 2.66GHz
CPUID Revision 000006FBh
Core Voltage 1.325 V

CPU Speed:
CPU Clock 3200.0 MHz (original: 2667 MHz, overclock: 20%)
CPU Multiplier 8.0x
CPU FSB 400.0 MHz (original: 333 MHz, overclock: 20%)
Memory Bus 400.0 MHz
DRAM:FSB Ratio 1:1

CPU Cache:
L1 Code Cache 32 KB per core
L1 Data Cache 32 KB per core
L2 Cache 4 MB (On-Die, ASC, Full-Speed)

Motherboard Properties:
Motherboard ID 04/02/2008-P31-ICH7-6A79OG0YC-00
Motherboard Name Gigabyte GA-P31-S3L (3 PCI, 3 PCI-E x1, 1 PCI-E x16, 4 DDR2 DIMM, Audio, Gigabit LAN)

Chipset Properties:
Motherboard Chipset Intel Bearlake P31
Memory Timings 5-5-5-18 (CL-RCD-RP-RAS)
Command Rate (CR) 2T
DIMM2: Corsair XMS2 CM2X1024-6400C4 1 GB DDR2-800 DDR2 SDRAM (5-5-5-18 @ 400 MHz) (4-4-4-13 @ 270 MHz)
DIMM4: Corsair XMS2 CM2X1024-6400C4 1 GB DDR2-800 DDR2 SDRAM (5-5-5-18 @ 400 MHz) (4-4-4-13 @ 270 MHz)

BIOS Properties:
System BIOS Date 04/02/08
Video BIOS Date 01/29/07
Award BIOS Type Award Modular BIOS v6.00PG
Award BIOS Message Intel P31 BIOS for P31-S3L F7d
DMI BIOS Version F7d

Graphics Processor Properties:
Video Adapter Gigabyte GeForce 7300 GS
GPU Code Name G72GS (PCI Express 1.0 x16 10DE / 01DF, Rev A1)
GPU Clock 680 MHz (original: 550 MHz, overclock: 24%)
Memory Clock 472 MHz (original: 400 MHz, overclock: 18%)

See if there is a newer BIOS available. You may have faulty ram that can't run at specified timings. And your PSU is a ?

Run MemTest86+ and see if your RAM passes it. It should take about 1HR at most. It may be time to upgrade your motherboard to something more willing to overclock. I've read good things about P45, X38, and X48. I wouldn't upgrade to a P35 from a P31.

Agreed with Memtest86+. Also just pop in a new battery. I had smiler issues of settings reverting to stock on a few motherboards, it turned out to be a battery issue. Imo, if Orthos was stable for 8+hrs RAM issues seem unlikely.