As an aside, if this is for a toolbar button, you might want to take advantage of the "Three-Button" capability, which would let you left click the button to open the selected file/program on desktop 1, and right-click it to open on desktop 2, or middle-click to open on desktop 3, without extra prompts. See Multiple Function Buttons for details if that sounds useful.
Hmmm tried your versions, but all (so it seems) with the same result: some programs work, while others fail and it does not seem related to the use of spaces in names