- your memory timings aren't set too low. if you run fast memory at a slower speed (like yours is), it's possible to lower the latency values in the bios for performance... but in order for it to work at a faster speed, you might have to turn up the latency a little bit. if you haven't messed with the timings at all, then disregard this.
- your fsb isn't overclocked much. a, say, 140mhz fsb would equal 175mhz (350mhz ddr) memory and it probly won't be able to go that high. if your fsb is upped, bring it back down to 133.
i'd do benchmarking and see which configuration is best. believe it or not, it might be better to have the memory run syncronously with the fsb (133, 1:1) and have low latency timings than to have 166mhz memory with higher timings.