Snapshot doesn't create backup

Hi. I have installed Snapshot on a website, but the backup doesn’t run when scheduled or when ‘run now’ is clicked. No details are shown in the Archives column on the All Snapshots page. There are no error messages displayed (even when WP_DEBUG is set to true). The Server Info shown under Settings is:

WordPress Version 3.5

PHP Version 5.2.17

MySQL Version 5.0.96

Is Multisite No

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: /tmp

Session save path is a valid directory.

Session save path is writeable.

Folder Permissions Writable (0755) – /wp-content/uploads/snapshots

Writable (0755) – /wp-content/uploads/snapshots/_backup

Writable (0755) – /wp-content/uploads/snapshots/_locks

Writable (0755) – /wp-content/uploads/snapshots/_logs

Writable (0755) – /wp-content/uploads/snapshots/_restore

PHP runtime information

Display Errors 1

Error Reporting 4983 – E_ERROR, E_WARNING

Magic Quotes 1

Max Execution Time (seconds) 180 The value displayed can be adjusted by Snapshot PHP scripts.

Memory Limit 40M – WP_MEMORY_LIMIT defined by WordPress wp-config.php.

Open Basedir Off

Running PHP in Safe Mode Off

ZLib Compression Off