Scheduled Task Fails.

I've schedule a task (shutdown - not the MS version) to run at a certain
time. When I run this program "Manually" all works well. However the
schedule task fails.

The account I use has admin privs, but DOES not have a password. I suspect
that is the issue.

Having said that, I run WinTvPVR and have serveral scheduled recordings that
run under the same account without fail.

What am I missing?

(System: WinXP, SP2 etc.)