On my Pogoplug I # installed Debian, and it's running as a web server very sucessfully.

I have installed a web based Home Automation app, called homeautomation, which executes schedules as AT jobs submitted as the www-data user.
The jobs do not complete and just get stuck in the running state.
The only error I see is in the syslog which reports an authentication failure
This is the case regardless of what job I try to run.
Running the job as root is OK.

I have checked that www-data is in the at.allow and cron.allow, and not at.deny and cron.deny, and the account has a shell assigned.

does anyone have any idea what might be going on and how I can fix it.

I don't see userid www-data anywhere in that authentication failure message. Are you sure they're running as ww-data?

It's also possible these particular scripts are looking for a userid/password. You can find out by sudo-ing to the www-data userid and running them from the command line.