There are 2 situations:
1) Your RAM is at limit here. Try setting it to a fixed 800MHz frequency in BIOS, or change the RAM multiplier to give you something around 800. Then try going over that 229 clock that you reached.
2) You could have hit the maximum frequency of the CPU for that voltage. So up the voltage or be satisfied with that.
I'd try to see if it's situation 1) first.