hi, what is the stability of your card like? what os are you running on and which version of catalyst and amd sdk? i found this thread the other night https://litecointalk.org/index.php?topic=3648.0

i know it relates to the 7970 card but the driver version may have the same effect on the 280x

i have just purchased sapphire's version of this card, im just waiting for a couple of components before i can start experimenting

719kh/s seems pretty good to me though