I'm running the latest GUI Miner with no problems. You should try w256 then f1. Do some stable overclock and such. Even try the Phoenix Miner.
-w256 slows it down even more (about 15Mhash/s) like 6/9 version. f1 doesn't do anything except lag the desktop. I even made a new folder for 6/14 version and re-did all the settings and setup new miner, doesn't change anything. Runs significantly slower still.