Security context may be the answer to your problem.
When you logon to MODCLEV and run the .bat it is running as you (admin). And it doesn't involve scheduling to do stuff on other computer. That's why it works. But when you use AT, it isn't the old AT anymore.
As soon as you install IE 4 or 5, I think 5, your schedule service (control panel->services) which uses atsvc.exe from system32 folder has been completely replaced. With this old schedule service you can change the startup, logon as in control panel. You can schedule your service as any particular user.
Now, after IE installation, you have a new service called task scheduler which uses mstask.exe from system32 folder. If you check the service's startup in control panel -> services, the logon as is gray out w/o option to change. Now everytime you schedule something (AT, WINAT etc) you are running it as LocalSystem account which doesn't have ANY authority on the network (anywhere but local). So you can schedule anything (shutdown etc) to local and it will still work. But as soon as it involves shares on other computer, shutdown other computer, your LocalSystem account can't do squat. So, that's why MODCLEV cannot command anything to MOD16.
You can verify the security context by using "pulist" from resource kit.
Now, the solution. 1st, delete the task scheduler service and/or schedule service from MODCLEV (use sc or service installation wizard from resource kit). After this use the same tools (svc installation wizard is much easier) to add a service called "schedule" and the executable for the service would be atsvc.exe from system32 folder. Go to schedule service in control panel, services. Set startup to automatic, log on as to your domain admin account. You should be set now.
www.jsiinc.com and http://is-it-true.org/nt has more info.
Hope that helps and good luck. Email zaw@trdesk.com if it still doesn't work.