Hi Tib,
It seems you have durep installed for calculating where your disk space has gone but the script to updtae it (via cron) contains errors. Errors from cron scripts are emailed to root by default.
Try to work out what is missing in the script by looking at /usr/local/bin/durep with vi and checking the line numbers given in the error report.
Alternatively, try reinstalling durep to clear the errors (rpm -Uvh durep.whatever.rpm).
Damian