Yesterday Apple issued a supplemental update for OS X 10.6.7 that addresses a few hangs that owners of the 13-inch MacBook Air (late 2010 model) were experiencing after applying the initial OS X 10.6.7 release. The hangs happened when users would play and manage music in their iTunes libraries, and was caused by an error with how protected audio files were being handled.
The update is a small 461KB patch that addresses compatibility issues with the AppleUpstreamUserClient and AudioAUUC system components, which are extensions that help manage protected audio content. It should be available via Software Update for Macbook Air systems, but is also available as a direct download from Apple's Support Downloads site.
The update requires that you have the latest OS X 10.6.7 update installed, so be sure you update your system before installing this patch.