Apple appears to have resolved the problems where 15-inch Mid-2010 MacBook Pro computers may intermittently free or stop displaying video.
The resolution has appeared in the form of a software update that is available now.
The symptoms of the problem described by Apple are:
Apple has determined that a small number of MacBook Pro (15-inch, Mid 2010) computers may intermittently freeze or stop displaying video on the built-in display or on an external display connected to the MacBook Pro. In this situation, you may also see a restart warning message before the video is lost or the display turns black or gray. Affected computers were manufactured between April 2010 and February 2011.
Additional information about the update can be found at http://support.apple.com/kb/TS4088.
Download the update directly or check for it in Software Update on your Mac.