I went to the .75 beta because of this statement in the release notes:
Improved performance of the graphics memory manager on GeForce 8 series GPUs running DirectX 9 applications in single-GPU configurations.
These improvements solve cases of reported performance slowdowns in some 3D applications with high graphics settings and resolutions.
I got the black screen this time. But, after reboot, the new drivers are up and running just fine.
Strange issue.