I see. You may want to wait for the new driver's from Nvidia. I, too, don't like driver issues.
Have you had these issues ever since you got the cards or SLI?
Have you tried one card in the computer at a time? Just to make sure both are working properly.
Here's the funny part. I had a co-worker that suggested me to try that which I did. After testing both of them one by one they worked fine, and I placed them back together with SLI and the problem was solved for like a couple of weeks. You think it might be heating issues?