I have troubleshot many many many cronjob failures over the years. In the case where it runs when manually invoked from the commandline, but not when invoked from cron, it has ALWAYS turned out to be an environment problem or permissions problem, just like Guttorm has already said.
From a command prompt, as the userid that you want to run the cronjob from, run "env" and trap it's output to a file. Then create a cronjob using this same userid and have it run "/usr/bin/env > /tmp/my.cron.env". Notice that I put the fully qualified pathname to the "env" command in that cronjob. /usr/bin would probably(?) be in a normal cronjob's environment, but why take chances? It's good form to be 100% explicit when messing with cronjobs.
After the cronjob has executed, compare the two environment files. Look for something that is missing that your job might require.
Last edited by haertig; 01-19-2007 at 02:55 PM.