My app was working in the iPhone simulator yesterday. Today I made some small changes to the viewController nib file that contains a few images and controls - mainly I changed one image and deleted some views. I added some replacement images into the Resources folder that get used in the window setup at startup. The app loads fine. It reaches the end of viewDidLoad and the window displays in the simulator - then immediately closes. I get 2 messages in the Debugger console: ************* dyld: Library not loaded: /System/Library/Frameworks/UIKit.framework/UIKit Referenced from: /Developer/iPhone Apps/App name/build/Debug-iphonesimulator/App name.app/App name Reason: image not found The Debugger has exited due to signal 5 (SIGTRAP).The Debugger has exited due to signal 5 (SIGTRAP). *********** If I run a different app that this current app was copied from it works fine. All the build configurations are identical. I don't know what "image not found" would mean. All my images are there in the actual project directory and the Resources folder in the project list. They are all named correctly . None of that changed since the last time the app was working. Why does it say it can't it load the UIKit frameworks? If the other apps can load why not this one? The programs are nearly identical.