The "Run" dialog doesn't seem like it provides redirection at all. I guess that the parameters are all being passed to Powershell, which chooses to redirect if it's not receiving encoded input? Sounds like a question for Raymond Chen.

This works, at the expense of spawning a command prompt:

cmd /c powershell -EncodedCommand IAA1ACsANwAgAA== > c:\ps.txt 

The "Run" dialog doesn't seem like it provides redirection at all. According to this usenet post you only get redirection if you have a console. I wonder if the redirection parameter is being parsed by powershell.exe, which is choosing to redirect if it's not receiving encoded input? Sounds like a question for Raymond Chen.

Anyway, this works, at the expense of spawning an otherwise useless console:

cmd /c powershell -EncodedCommand IAA1ACsANwAgAA== > c:\ps.txt