That RAM should do 233, my Corsair XMS does 245, although it doesn't like much higher than that. Have you tried increasing the RAM voltage slightly (eg from 2.6V to 2.65V or to 2.7V) This might help you RAM be stable at higher speeds.
One more thing, what is your stepping? It may be that you have a poorer stepping than some, and oyu might have reached your CPU's limit. Also, letting it burn in for a week or so of use, from what I've found, can help loosen it a little, and allow you to clock higher. I could get max of 2.6, left it for a week or normal running, and last weekend got 2.7 out of it with a 333 divider on my RAM.
a lot of the time instantaneous overclocking thats stable will not happen! Be patient, and keep trying