Either (a) the audio file is corrupt, or (b) the audio file name contains an illegal character for the Mac OS, or (c) the file may have been created from an older version of Media Composer or (d) the file may have been created from an AudioSuite Function performed within Media Composer.If the file plays and previews but does not process from an AudioSuite function, the simplest solution may be to solo the track the region is on, Bounce to Disk and reimport the file, spotting to original time stamp.Check the file name of the audio file. It seems that Post Conform doesn't know to disallow certain characters in filenames that Pro Tools hates. The characters : ; \ and / are problematic. Check the Media Composer version to make sure it is the most recent, and verify if AudioSuite functions have or have not been performed on the audio file while within Media Composer. There were a couple of versions (specifically 7.0 through 7.2) that had broken OMF export functions. Also, if these files were processed at all with Audiosuite plugins while in Composer problems are likely because Audiosuite could potentially create a sample accurate file inside a frame accurate application (Composer). Composer would be forgiving about this newly created file but when that file hit another app (Pro Tools) it would not behave correctly.