Without more info, there's not much anybody can do except recommend some settings. How long have you been mining on the pool at that speed? Are you getting hardware errors? What's your accepted:rejected ratio?
I have two 7950 cards running @ ~ 343 Kh/s each. My settings can be found here:
https://bitcointalksearch.org/topic/m.5597962
I copied your conf file, put my information, and it's giving me the best kh/s I've gotten, by far. Both my GPUs are also working. Very nice.
Nice! Glad that I could help!
I noticed that the pool was not taking anything from my second GPU, but non the less, it's still much better than before. I'll try to figure it out.