Powershell – Scheduled PowerShell task won’t write to file

I have a PowerShell (PS) script I want to execute every day at 5:00 a.m. I want to run it to run automatically, so I scheduled it via the Task Scheduler (running Windows 7 Ultimate with SP1, 64-bit). As a test, I wrote a simple PS script that just appends to a text file with a time stamp. It runs–I can see the PowerShell window open and it writes out the PS log–but it doesn't write to the text file.

The script runs fine from the command-line, and from the PS shell. It doesn't work from Task Scheduler, either from the scheduled time or just from the Task Scheduler list and right-clicking and selected Run. Both times it runs, but doesn't write to the text file.

In Task Scheduler, I have the "Actions" set to Start a program, PowerShell.exe. For the "Add arguments", I have:
-NoProfile -ExecutionPolicy Bypass -Command C:\AccessTask\ATestScript.ps1

The script is simplicity itself:

Start-Transcript -path "C:\Temp\aTestScript.log" -Verbose

write-output "Start";

# just write one line to file
write-output "Logging";
$text = Get-Date
$text >> 'aTestScriptOutput.txt'

write-output $error[0] | fl -force
write-output "Quit";

Stop-Transcript

Is there something special I have to do to allow a scheduled task to write to a text file?