I`m using rsyncbackup, http://code.google.com/p/rsync-backup/, as my central backup solution. I`ve configured everything and it works fine when I run it manually, but over some servers it wont run over cron.
I think its a PATH issue so Im asking is there any way to debug this and find out which part of the script wont run?!

Start with looking in /var/log/syslog to see if cron generated an error message.

Did you include the path to perl in the cron job? Did you enter the cron job in /etc/crontab and specified that it should run as root?

Are you calling the script just by the script name (/path/to/script) or are you calling perl explicitely like:
/usr/bin/perl /path/to/your/script
The latter is the correct way.

There is an option to increase verbosity in this script. Use it, and redirect your output to a file in your home directory or the /tmp directory.
/usr/bin/perl /path/to/your/script > /tmp/backup.log

jlinkels