I have the same video card. I'm no expert as I just started mining LTC 1 month ago, but I typically get 140 kH/s on intensity 12, which allows me to use my computer while mining. I've heard of people maxing out this card around 200 kH/s, but I haven't tried.
Go ahead and post some screen shots and I'll see if I can help.
I think it could have something to do with my driver. Whenever I start reaper, my display driver crashes and recovers, but then my kH/s plumits. I'm on 13.1.
I changed the clock speed so that it is about a .7 ratio but it didn't seem to help. Also, I'm not sure if my graphics card is actually being utilized fully. I have a Gigabyte card and when I open OC_GURU (their afterburner) on the monitor it says GPU 300 MHz and Memory 150 MHz. So maybe it isn't scaling up the GPU?
I also looked in CCC and my GPU OverDrive is enabled. Could this interfere with anything?
EDIT
aha! I think the GPU OverDrive wasn't activating since I was on Balanced instead of High Performance (windows thing). Will report back!