Hi Brian, its time to get a Mac (just kidding).
I'm sorry to hear it's not working for you. Please try this one:

script: var factory = moi.command.createFactory( 'box' ); factory.setInput( 0, moi.vectorMath.createFrame() ); factory.setInput( 2, 20.0 ); factory.setInput( 3, 20.0 ); factory.setInput( 4, 20.0 ); factory.commit(); moi.view.resetAll;

The inputs require floating point numbers and that's the only "Type mismatch" I see. Maybe Windows is more picky than Mac.
Another thing to try is to put standard quotes around box like so: "box"


Also if you put the script into a .js file you should leave out the word script: at the beginning (I think).

I used the scripts successfully in version 2.5 and the newest 3 Beta.