I got mine to work after having this problem...maybe this will work for you guys as well. Start computer with main graphics card plugged in AND secondary graphics card plugged in. Launch miner with device set to 0, then unplug primary graphics card from monitor, switch to secondary graphics card, then run again with device set to 0. For me, it starts out with one of them using 25% CPU then it drops back down to 0% after I launch the second miner... I have no idea why this works, but this is how I fixed the problem.