Try flipping around the SLI bridge.
Link to Evga forums about a customer going all crazy on evga when his 4x gtx 580's SLI wasn't working (sorta the same issues your having) and soon to find out that his SLI bridge was installed backwards.
4x SLI 580 Black OPs Edition in SR-2 causes the Nvidia driver to crash I am totally bummed
Go to page 9 for results.