I ran in to something really odd. I have been using crontab for LONG time and never seen this issue before. Basically I added new entry into my crontab by type
crontab -e and as always saved/exited. For some reason that command never ran at the time I specified. I tested few more times and no luck. So I started looking on google to find out why crond will not ready my new entries from crontab. And then while I was looking, I decided to restart crond by issuing: service crond restart and to my surprise, my new schedule started working.
While I was looking around for solution for this problem on Google, I came upon few pages where they talked about if you have empty line before command, that command will not work. For example:
#this is a cron file
* * * * * /do/something
In this example, /do/something will not run since there is a blank line before it. You can fix this by moving that command up or put another comment above it. This is a very odd thing and I have never experienced it myself but I figured if you stumble upon this post looking for help, blank line before command in crontab might be your issue. Please comment if you had to delete a blank line to fix your crontab file. Also mention which OS you are using. To learn more about crond, see man crond and man crontab.