(Sql05) SSIS Execute Process Task Hidden WindowStyle Not Working

I'm having a problem with an Execute Process Task in SSIS (SQL2005).

I set the WindowStyle property to 'Hidden', which worked fine until I assigned a variable to the StandardOutputVariable. For some reason, having a StandardOutputVariable assigned overrides the WindowStyle property and displays the command window no matter what.

Is there any way to force the window style to be hidden, and still capture the standard output?

Thanks.