Every 2 Minutes cronjob

This is my crontab file: # m h dom mon dow command */2 * * * * /sbin/scap 30 00 * * * /sbin/dzbu 30 06 * * * /sbin/dzbu 30 12 * * * /sbin/dzbu 30 18 * * * /sbin/dzbu 37 * * * * /sbin/cleanpng The first cron job (scap) does not seem to be being started. However dzbu does get started. Running scap from the command line works fine. Any ideas as to what I am doing wrong? Thanks David