Users of last year's MacBook Pro models with NVIDIA GPUs are finding the upgrade to Lion to be far less than perfect. Problems in the NVIDIA graphics drivers that shipped with OS X 10.7 appear to be at the root of kernel panics and system freezes that leave an affected MacBook Pro with a blank black screen. Though Apple wouldn't confirm the issue directly to Ars, support engineers appear to be actively investigating the issue. For now, rolling back to Snow Leopard appears to be the best option.

Numerous reports of crashes have filled an Apple Support discussion thread that sprung up July 20, the same day Lion became available via the Mac App Store. Since then, several crash reports posted to the discussion show a clear pattern of crashes happening in drivers for the NVIDIA GT330M that shipped in 15" and 17" Arrandale-equipped MacBook Pros with switchable Intel and NVIDIA graphics.

Some symptoms of the problem include repeated kernel panics, a screen that suddenly goes black, or the inability to wake from sleep. The specific cause isn't clear, but a variety of graphics-related functions seem to trigger the problems, including switching on the NVIDIA GPU, switching to internal or external displays, and running certain GPU-intensive operations in various applications. In some cases, a black screen can recover by switching between internal or external displays. Some users have also reported success in using the open source utility gfxCardStatus to force a system to use the integrated Intel graphics and/or disabling sleep to prevent the problem from happening.

The problem apparently affected Lion during its beta testing by developers, and users are frustrated that the issue made it all the way to the shipping version of Lion.

Apple did not respond to our request for comment on the matter, but several users said that support engineers are actively investigating the issue and collecting crash reports from users that contact Apple Care.

Aside from the aforementioned method of forcing a MacBook Pro to use the Intel IGP with gfxCardStatus, which doesn't appear to work in all cases, reinstalling Snow Leopard unfortunately appears to be the best strategy to alleviate the problem until Apple has a fix ready.

UPDATE: A commenter noted that Apple Care support technicians have offered another solution which appears to have permanently solved the problem on his machine. Navigate to ~/Library/Preferences/ByHost/, delete any files that contain "windowserver," and reboot the machine. The procedure may need to be repeated if you regularly connect to an external monitor once it is also connected.

Note that the user Library folder is hidden by default on Lion. You can get to it by holding down the Option key in the Finder's Go menu, use the Go To Folder command and paste in the full path, or use Terminal to make your ~/Library folder permanently visible.