This error is caused by file corruption during the uploading process.
It is very important that all files be uploaded in binary format only, meaning that your FTP client cannot be set to automatically detect the appropriate upload type. The reason for this is that the files are encoded (for Zend or Ioncube), and are therefore comprised of binary data even though their file extension (.php) would seem to indicate that they are plain text.
Reuploading the files in binary mode should correct the problem.
