Apple released an update to Mac OS X 10.6, saying that it will fix the early 2011 MacBook Pros that were facing problems with graphics stability and external display compatibility. Many users were finding that their MacBook Pros (bought in early 2011) were freezing under heavy load, for instance while encoding a large video file. The flickering issue seemed to be a problem with MacBook Pros that are equipped with Thunderbolt when connected to Cinema Displays.
The software update highlighting improvements
Mac OS X 10.6.7 (the update) does fix the freezing and flickering issues, in addition to improving the reliability of Back to My Mac, resolving an issue when transfering files to certain SMB servers, addressing various Mac App Store bugs and addressing minor FaceTime performance issues.