I'm using a MacBook Pro 17" OS X 10.7.4 with 2.66 GHz Core 2 Duo processor, 8GB RAM, 1TB HD with 650GB free. I get the problem with all video files but I mainly watch .avi and .mkv - from 1080p/720p down to 512 x 288px. I am using the MacBook Pro's built in speakers. The problem started for me...