I can confirm that this driver does indeed fix the issue that I too was seeing with -current (jun 20th kernel). Whew! Now I don't have to fsck 300Gb of disk each time I exit Xorg
Curiously as I dug into things I realized that x11/nvidia-driver is a port of the 96xx series driver but not this "bleeding edge" driver. I'm not sure why. I haven't asked the ports mailing list yet. But as Zander helpfully said, the driver compiles and runs flawlessly on -current (as of Jun 22 kernel), so the stage is set for success once 7.0-CURRENT -> 7.0-RELEASE "real soon now."
Thanks Zander for your input on this thread!