Snapshot works on database tables but does not save files

Hi Guys I'm having a bit of trouble with Snapshot; it does not save the files (blogs_dir).

Thanks for any help!

Nick

Some info:

- all tables get to 100% on making the snapshot, except 'files' which stays 0%

-WordPress Version 3.5.1
PHP Version 5.3.10-1ubuntu3.6
MySQL Version 5.5.31
Is Multisite Yes, Number of Sites: 36
WP_CRON Snapshot uses WP_CRON to run automated backups. If you have disabled WP_CRON via your wp-config.php you will not be able to schedule snapshots.
WP_CRON Enabled.
_SESSION Snapshot uses _SESSIONS to store temporary information about database tables and files during the backup and restore processing. Sessions are a default part of PHP.
Session save path: /var/lib/php5
Session save path is not a valid directory.
Session save path is not writeable.
Folder Permissions Writable (0771) – /wp-content/uploads/snapshots
Writable (0771) – /wp-content/uploads/snapshots/_backup
Writable (0771) – /wp-content/uploads/snapshots/_locks
Writable (0771) – /wp-content/uploads/snapshots/_logs
Writable (0771) – /wp-content/uploads/snapshots/_restore
PHP runtime information
Display Errors Off
Error Reporting 4983 - E_ERROR, E_WARNING
Magic Quotes Off
Max Execution Time (seconds) Off The value displayed can be adjusted by Snapshot PHP scripts.
Memory Limit 1G - WP_MEMORY_LIMIT defined by WordPress wp-config.php.