P35-S3G Overclocking problem

[alur]

I've been running my e8400 stable at 4ghz (9x445) since I got it almost 2 years ago. However, since I upgraded my old x1950 to a 5770 I've been unable to boot with even a 340 mhz fsb (a mere 7 mhz overclock). Before I run through all the things I've already tried, here are my components:

Motherboard: Gigabyte GA-P35-S3G (bios version F5)
CPU: Intel E8400
Ram: 4x G.Skill F2-8500CL5-1GBPK (1GB 5-5-5-15)
Graphics Card: H577FM1GD Radeon HD 5770
Power Supply: Antec Smart Power 500W

Now here's what I've already tried booting with at 340mhz fsb (without any success):
- Without any harddrives or cdrom drives connected to the PSU
- With the F2 and F3 bios versions
- With an Antec TruePower 750W PSU
- Tons of bios/voltage combinations
- With only 1 ram stick connected
- Without any USB devices (except the keyboard)

I also have the same problem when using my friends Radeon 4870. The interesting thing is that, assuming that I set the voltages and memory multiplier correctly in bios, I can use easytune to clock the cpu to 4ghz, and it's stable in every test I've thrown at it. However, I'd much prefer to avoid using Easytune as, among other things, it takes forever to load and then gives me a "Could not load the device driver" error (might have something to do with Windows 7) before appearing in the system tray.

When the boot fails the screen turns on for a few seconds (if I use the HDMI connection, not with the DVI connection) and then the video card fan spins up extra just as the beginning of the "Testing Memory" is printed out before the computer shuts down and reboots with the FSB control disabled and the memory multiplier set to auto.

So... any ideas?

[oggmonster]

The only thing I can think of would be a northbridge voltage increase? But sounds like you have tried that already?

[alur]

Yes, I've already tried overvolting that as high as the bios will let me :p

[oggmonster]

I know you said you would prefer not to use easytune but have you tried using it just out of interest. Sounds like you may have to RMA the board to me? 

[alur]

Well, yes. I've been using Easytune for a couple of weeks now. I'm just not a big fan of having an error message appear on boot, and of course the CPU runs at default clocks until I get into Windows  :p

Oh well, I suppose I can manage until I decide to upgrade my system again