P6N SLI V2 sometimes doesn't post

I'm having a strange problem with my home-built PC. It sometimes doesn't post. The circumstances are as follows:

* It sometimes doesn't post when I turn it on, but usually it does.
* It *never* posts after a soft reboot (by the OS) or a hard reset (with the reset button)!

When it happens, the symptoms are that it hangs before even initializing my SATA devices or the video card, and there are no beeps. Basically all that happens is that the fans rotate, so it's hanging somewhere very early on in the process. But it can't be a structural problem, because sometimes it does boot and when it does all my hardware appears to be functioning perfectly!

My hardware is as follows:

MSI P6N SLI v2
2 x 1 GB Nanya 800 MHz DDR2
Intel QX6850 Core 2 Extreme 3 GHz
EVGA e-Geforce 8800GTX 768 MB
2 x 500 GB SATA disk
SATA DVD writer

I hope somebody here can give me some ideas as to what could be causing this strange behaviour?

 

Never mind, it's working now. I loaded the default settings in the BIOS and that did the trick, no idea why, but I'm glad it worked.