Failed to launch simulated application: Unknown error

Question

• OS X 10.5.7 (genuine Mac)
• Xcode 3.1.3
• iPhone SDK 3.0

When I try to execute my iPhone application in simulator, I get the dreaded error

Answer 1

I had a similar issue. I was also unable to install the app on a device, getting a 'The application bundle does not contain a valid identifier." error message. This was due to a directory named "Contents" added as a Folder Reference. I removed the reference, renamed the directory, add it again as a Folder Reference, clean the project, rebuild and voilà, I was able to launch the simulator.