I'd go ASUS, why do you need their tech support when you got us
However, this doesn't seem like a motherboard problem. You could try booting the system with each stick of RAM individually that will rule out it being a RAM problem. I'm guessing you were overclocking the processor? I don't recall a 2.9Ghz P4. have your tried taking the heatsink off the processor wiping all the old thermal paste off with a coffee filter and reapplying Arctic silver? I personally believe your processor is getting too hot or your video card is dieing. You could always buy a new video card from a place that will take it back if it doesn't solve the problem... and while you're there pick up some Arctic silver, they sell it at COMPUSA.
If you were overclocking try resetting the cmos as that should set the CPU back to factory speeds and possibly solve the problem.