ARD Scheduled Tasks Failing

My network has 10.6.8 Intel Macs.

These Macs have ARD Client 3.5.3.

I use ARD Admin 3.5.1 (461.1) Unlimited on a 10.6.8 v1.1 Unlimited Server to manage weekly software updates using the following Unix command,

COMMAND_LINE_INSTALL=1; softwareupdate -i -a; diskutil repairPermissions /; shutdown -r now

Problem:

Clients never finish the weekly update task. I can see in the ARD logs that the software update and repair permissions finish, yet in the open Task status window the clients show as "Running" and the machines haven't restarted. So it looks like for some reason the "shutdown -r now" command isnt working.

Troubleshooting:

I use ARD Admin 3.5.1 because I upgraded other admin systems to 3.5.2 and 3.6 and lost functionality for running reports and various other items. So I'm sticking with ARD Admin 3.5.1.

I made 2 separate tasks - 1 ARD Unix task for the software update (COMMAND_LINE_INSTALL=1; softwareupdate -i -a; diskutil repairPermissions /) and 1 ARD built-in task to restart machines.

Now with my troubleshooting tasks in place, the first software update task still hangs on seemingly random systems as "Running..." and never runs the queued task to restart ARD clients.

Is there a way to timeout tasks for individual machines, so that if the task sits running on one client for more than say 15 minutes, the task moves on to the next client and then on to the queued client restart task?

Or do you know of a better way to get updates run and machines rebooted every week?

Thanks in advance for any assistance.