[COLOR=#303030][FONT=monospace]/System[/FONT][/COLOR] [COLOR=#303030][FONT=monospace]/sbin[/FONT][/COLOR] [COLOR=#303030][FONT=monospace]/usr (with the exception of /usr/local subdirectory) [/FONT][/COLOR]
Not sure if anyone else encountered this issue after upgrading to ML, but kept getting a "Valid DVD Drive could not be found -70012" when playing a DVD or Blu-Ray disc on drives previously working in Lion.
To fix this error, run the following commands in Terminal:
Step 1 - Create a backup of DVDPlayback.framework
sudo cp /System/Library/Frameworks/DVDPlayback.framework/Versions/A/DVDPlayback /System/Library/Frameworks/DVDPlayback.framework/Versions/A/DVDPlayback.bak
Step 2 - Patch DVDPlayback
sudo perl -pi -e 's|\x49\x6E\x74\x65\x72\x6E\x61\x6C|\x45\x78\x74\x65\x72\x6E\x61\x6C|g' /System/Library/Frameworks/DVDPlayback.framework/Versions/A/DVDPlayback
Now playback, eject, and auto sleep should be working again. If these steps don't work, try copying the DVDPlayback.framework from a working Lion installation, then run the commands. Good luck!