In one case these errors were caused by the user saving Pro Tools sessions and audio files into a Digidesign Databases folder on the hard drive. Removing these files from the Digi Database folder fixed this problem.

•Note• There should only ever be no more than the 2 files that Digidesign automatically places in this folder. This folder is used by Pro Tools to archive and manage the file system of your hard drives and should only have the Volume.ddb file and the WaveCache file inside.