auto shutdown stopped working true Image Home 2009

I have searched and found how to set up auto shutdown after daily backup, here http://forum.acronis.com/forum/5303

I have true image home 2009 on Windows XP Pro

I set up the auto shutdown after the first full backup, about a week ago and after the first incremental backup the PC did shutdown, but has not done so since.

Why did auto shutdown work once and then stop?

I have checked and it is still set as -
Command: shutdown

Working directory: C:\Windows\System32\

Arguments: -s

I found a comprehensive list of commands in post#5 at the url -http://www.wilderssecurity.com/showthread.php?t=226406
but I have no idea where to put all that code, I'd appreciate any help on trying that. I build websites and understand html css some js and php but i don't know anything about this stuff.

I don't really see why there can't simply be a button to select, instead of entering commands, because auto shutdown after backup seems to be so obvious a need. I set the backup to run at 6.30pm , a time when I am not using the pc.