Don't know...
I downloaded your little VI and (after changing the name of the program to launch to Notepad.exe), built it into a standalone program and everything worked as expected: Clicked the "Program" button and Notepad opened...
(By the way, nice panel design...)
How exactly are you building it into an executable? Are you using the option to save the subvi's in a seperate library? If so that library needs to be in the same directory as the .exe .
Otherwise I would say you are doing everything right. Attached is the build file my app builder (V6.0.2) created, and the application it created. See if it works for you...
Mike...