So I downloaded and installed the new iPhone 3.0 SDK and when I returned to developing my apps when I would make a change, then hit “Build and go” I would get this error in the organizer: “The application is already installed on the device”. I would have to manually remove the app from within the Organizer then hit Build and go again and it would install just fine and move on.

I noticed In the organizer Console tab this is what appears:

unknown mobile_installation_proxy[334] : preflight_application_install: The application has already been installed
unknown mobile_installation_proxy[334] : install_application: Could not preflight application install
unknown mobile_installation_proxy[334] : handle_install: Installation failed

So I went to iPhone Dev center and downloaded my provisioning profile again and dragged it from my desktop onto the Xcode icon. Opened up Xcode and was able to “Build and go” like I used to.

This Page showed me the light