My .mp4 movie files will open in Quicktime on my Mac when stored on any other USB flash drive. When I use my SanDisk Cruzer with SecureAccess and try to open an mp4 file, I get a Quicktime message that “The movie’s file format is not recognized.” Subsequent attempts to open any of the MP4 files ends with a “File or folder not found” message. Is this a known issue that is being resolved?
Did you save those files in Secure Access? In this case, the files are encrypted. When running them through Quicktime, it will not recognize it as mp4 file. Therefore it will not play them.
Copy the file onto the flashdrive, without using Secure Access and try playing them again. See what happens 
