A 500GB USB hard drive exhibits very strange symptoms; if you save a movie to the drive, the movie will only the last 5 minutes. The drive reports correct file sizes and disk capacity, and other files present on the drive are not affected. What could possibly cause this? You won't believe the answer:
http://blog.jitbit.com/2011/04/chinese-magic-drive.html
http://blog.jitbit.com/2011/04/chinese-magic-drive.html