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'm worried about these two lines:

12.08.09 11:01:28 com.apple.launchd[166] (com.apple.iPhoneSimulator:com.apple.apsd) Path monitoring failed on "/var/mobile/Library/Preferences": No such file or directory 
12.08.09 11:01:28 com.apple.launchd[166] (com.apple.iPhoneSimulator:com.apple.dataaccess.dataaccessd) Path monitoring failed on "/var/mobile/Library/Preferences": No such file or directory

It appears to me like your Xcode (specifically, the iPhone Simulator) installation is broken somehow. I'd suggest saving all your important files and reinstalling the SDK.