What bios are you using? Did you flash to the 3402? I'm getting MUCH better stability after flashing.

Same setup as you (cept I have the Kingston PC3500). Before I couldn't get past 14x166. Now I'm at 12.5x180 w/ no problems so far. Also, did you add some active cooling the northbridge? I put a Vantec Iceberq on there and moved the stock NB heatsink to the SB.