The log suggests that the backup is looking for the configuration folder in the wrong place.
"open_basedir restriction in effect. File(/data/htdocs/w/wp-config.php) is not within the allowed path(s)"
[ Moderator note: Use the code button and not blockquote. ]
[INFO] BackWPup version 3.0.1; WordPress version 3.5.1; A project of Inpsyde GmbH developed by Daniel Hüsken [INFO] This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it under certain conditions. [INFO] BackWPup job: Standard Backup; DBDUMP+FILE [INFO] BackWPup cron: 0 5 * * *; Fri, 1 Mar 2013 @ 05:00 [INFO] BackWPup job started manually [INFO] PHP ver.: 5.3.2; apache2handler; Linux [INFO] Maximum script execution time is 600 seconds [INFO] MySQL ver.: 5.0.95 [INFO] curl ver.: 7.15.5; OpenSSL/0.9.8b [INFO] Temp folder is: /data/htdocs/w/workshopshed/wp-content/uploads/backwpup-e3ce3-temp/ [INFO] Logfile folder is: /data/htdocs/w/workshopshed/backups/logs/ [INFO] Backup type is: archive [INFO] Backup file is: /data/htdocs/w/workshopshed/backups/backwpup_1_2013-02-28_10-15-20.zip [28-Feb-2013 10:15:20] 1. Trying to make a list of folders to back up … [28-Feb-2013 10:15:24] WARNING: is_file(): open_basedir restriction in effect. File(/data/htdocs/w/wp-config.php) is not within the allowed path(s): (.:/data/htdocs/w/workshopshed