The cron tab format is as folllows.
m(0-59) h(0-23) dom(1-31) m(1-12) dow(0-6) command
And the format you are following is valid for a cron that is supposed to run every 2 minute.
for creating a cron you can use
which I am pretty sure you know.
Your prob may be caused due to some problem in cron. Try restarting the cron once using
svcadm restart svc:/system/cron
Let me know if this information helped you.