Gigabyte GA-P31-S3G - Reboot and Memory Issues

i've been meaning to ask this question for a while, but i don't reboot my computer much so i kept forgetting to ask.

i own a Gigabyte motherboard, the GA-P31-S3g and when i do a restart it will sometimes turn off the computer for a couple seconds and then turn it back on. as opposed to a normal reboot where it restarts but maintains power through the whole cycle. i have a very good power supply, a Seasonic 500watt so i doubt that's the issue. it's really annoying and i'll explain why in the next paragraph.

i've also had an issue with memory on this motherboard. it's specs say it supports 4GB, but when i get the reboot issue mentioned above... it also makes my computer lock up at the Post screen and will not go any further (the gigabyte logo menu). the only way i've found to resolve the issue is to completely turn off the power supply and then power it back on. then the computer boots fine with no issues. this is only an issue when i have all 4GB in, any other configuration yields no problems at all. i've tried all the dimm slots individually and they all seem to function fine on there own. as i've said it's only a reboot issue with the ram, other than that the ramm functions perfectly.

...would help to post RAM maker/part number & CPU type...

Meanwhile, here's someplace to start -

Begin by doing a "Load Optimized Defaults" at main BIOS screen;

"Advanced BIOS Features" page:
"No-Execute Memory Protect" to 'Enabled'
"CPU Enhanced Halt (C1E)" to 'Disabled'
"CPU Thermal Monitor 2 (TM2)" to 'Enabled' - set to max of 70°
"CPU EIST Function" to 'Disabled'
"Virtualization Technology" to 'Disabled' unless specifically using Microsoft virtualization technologies s'ware

"Integrated Peripherals" page:
"Legacy USB storage detect" to disabled unless booting from USB drive/stick - 'Enabled' can cause re-boot loops otherwise

"MB Intelligent Tweaker(M.I.T.)" page:
"Robust Graphics Booster" to 'Auto'
"PCI Express Frequency (Mhz)" to 100 (not 'Auto')
"Performance Enhance" to 'Standard'
"System Voltage Control" to 'Manual'
"DDR2 OverVoltage Control" to accomodate your RAM - base voltage is 1.8V; i.e., +.20 give you 2.0V; tends to run a little low, +.25V gives me 2.01 Vddr
"(G)MCH OverVoltage Control" to +.1