Are you sure you have set the FSB correctly. It should be 133Mhz. (Or 266Mhz Dual Pumped)
Your ram should be DDR333 or PC2700 (Same thing) to run the FSB in-sync with the Ram.
Also, check the memory latency settings. (If you have the option) Start with 3-4-4-11 and drop them from there if they can handle it. Also remember that it is not unusual for 'unbranded' ram to not run at it's rated frequency. (Having said that I have had cheap PC2100 do DDR400 at 2-2-2-5!!!)
Also, Is the PSU up to the job? You'll need around 350Watts for that system. (Don't forget that cheap PSU's are rated at unsustainable peak load, In other words, they often blow up under load!!!)
A couple of progs that may help you are Prime95 for CPU and Ram stability testing and Memtest86 for testing your Ram. You may simply have static damnage!
Also, try (if you have options in the BIOS) upping the Voltage on the CPU and RAM On the ram, don't go above 2.77V or +0.1v on the CPU core. This will give you more stability, but keep a close eye on the temps and load test (With 3dMark or Prime95) and increase incrementally using the smallest possible step.
What if everything is an illusion and nothing exists? In that case, I definitely overpaid for my carpet. -Woody Allen