Are using a Custom Action that launches a file that is distributed with your setup? Are you launching a file using the option in the Setup Complete Success dialog? If so try resetting to point at the file again and this error should go away. What's probably happened is that upi pointed at a file and then removed and readded it to your project. The Custom Action and dialog properties point at an internal name (which is what the error shows) and needs to be reset.
Chandima Rajakaruna
Macrovision Corporation