Here's what you can try - disable Crossfire, or at least use your 5970 in single GPU mode (you know what I mean), essentially disabling 1 GPU, and run only in "crippled" mode. See if it cures the stuttering. CrossFire and SLI are prone to stuttering problems (that's why I don't use both), synchronizing frame data from 2 VERY HIGH SPEED HIGH PERFORMANCE graphic processors can be a hit-and-miss business, it's normal to have a little bit of stuttering with CF/SLI, most of the users won't even recognize that it's there... (I'm one of those who can, and doesn't like it). IIRC Anandtech have covered this issue in the past (or is it another site? I forgot), go google it if you are keen to find out.