Cudaminer from Dec 1 doesn't work, at least on that hardware.  Downgrading to Nov 20 version fixed it for me.  Autotune also functions, and spat out K8x24 for me.  I'm running like so:

My amazon experimental setup, getting about 180kH/s combined GPU/CPU (which is obviously not going to turn a profit):

cudaminer -a scrypt -o $POOL_URL -u $POOL_USER -p $POOL_PASS -C1 -H1 -l K8x24
minerd -u $POOL_USER -p $POOL_PASS -o $POOL_URL -t 6