Last several weeks I've noticed my laptop screen sometimes not coming up out of suspend, though I was changing kernel versions a lot so I thought that was causing it. Just had the opportunity to ssh into the laptop during one of those moments, and I see the exact same error in Xorg.0.log.
I'm on 2.6.32 amd64 with driver 270.41.06. I'll give the suggested intel_iommu=off tip a try. If that doesn't work, I'm going to go back to one of the 190 series, that was the last time I was free of this other problem: http://www.nvnews.net/vbulletin/showthread.php?t=158091