If you have not done so already, delete the following code from the C:GPath function in gpmain.lsp:
(princ "\nThe gp:drawOutline function returned <") (princ PolylineName) (princ ">") (alert "Congratulations - your program is complete!")
You had been using this code as a placeholder, but now that gp:drawOutline is functioning, you no longer need it.