I'm using cgminer with one 7950, and lately I have been trying play with clock speeds. Every time I change the mem-clock, the hashrate will go up slightly (about 15Kh/s), and then drop back down to where it was (275Kh/s). According to GPU-Z, the speed is staying where I set it, so why is the hashrate going back down???

I am making the changes from the GPU menu of cgminer while it is running.