@Tom. Thanks for posting to my support site. These errors could result from a couple of different things. I think it could result from a server configuration. I think your files are being corrupted because you fopen_wrappers may be disabled or turned off in PHP. You are going to need to enable allow_url_fopen in your PHP.ini configuration. You do this by editing your PHP.ini file and placing:
allow_url_fopen = On
Please see the following for more information: http://us.php.net/readfile#refsect1-function.readfile-notes
Please let me know if this works.