So I'm running a 7950, core clock at 1135, and memclock at 1575. 21712 thread concurrency, 1 gpu thread, 1 vector, 256 worksize, and 18 intensity at 640 kh/s. Out of the 1880 shares accepted, 250 were stale/invalid according to guiminer. I am using the recommended trick to reduce DOA's yet I'm still getting so many. Any ideas?
Try lowering the intensity to 16. The hash rate will drop, however run it for a while and see if the % or stale/invalid decrease.