org.eclipse.core.internal.resources.ResourceException: Resource is out of sync with the file system: '//AndroidManifest.xml'. AndroidManifest.xml does not declare a Java package: Build aborted.

Ignore it, it's fucking bull.

Of course you can try the usual trick, which is to refresh the project... but if it doesn't work...

Most likely you have your emulator or phone up and running. Kill it, then delete the rows of errors in the error log and run as an android app again.