No screen display - NVIDIA GeForce 8500 GT driver issue?

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http://askubuntu.com – Installed Ubuntu 11.10 on a Gateway GT 5628 with a NVIDIA GeForce 8500 GT graphics processor. Was working fine until I attempted to update the driver; now, after boot I get a blank/black screen. How can I revert back to the unrestricted driver from a terminal? (HowTos)