Rsync X fine in Terminal in Finder but issues when run as cron…

I have an RsyncX script between two Xserves (one Intel, one original PowerPC model). The script works fine when logged in as Admin and run from the Terminal. However when run as a cron job, the data is synchronized as expected but the rsync process doesn't seem to quit. On both Xserves Activity Monitors, multiple instances of the process build up over time, hogging the processors. Manually running the script nicely launches, does its job then quits. I'm using an SSH tunnel between the two. Anybody got any ideas? Many thanks.