WELCOME TO THE FORUMS!!!
i was using a XP1700+ with 2x256Mb Crucial on my XP333-R, the fastest i ran the ram was at fast, everytime i tried Ultra the system hanged. but after i Fried my 1700+(going to get the RMA back on monday, muuuhahahaha

), i bought a TB 800 200FSB for the time being, so my memory is running at DDR200 now, but the good thing is, i'm now running my ram at ULTRA2 !!!2-2-2 at 2.6V!!! but i doubt they will stay at this setting when i switched back to xp1700+.
in your case, whats your memV running at? the stock is 2.5V, you can set it to 2.6 or 2.7 using the jumper, and there is an undocumented setting at 2.8V, you need to short the jumpers at (2-3) and (5-6). try increase the Voltage a bit, and see if you can push the FSB to 166(DDR333).
