I created my app on my MacBook Air and kept working with it there which was fine. Then I started working with a colleague who used another Mac (of course). Anyway, we share
clang can't locate your precompiled header file. Have you checked whether there is a file named SlideMenu-Prefix.pch in /Users/linus/Dropbox/Apps/My App/Projekt/My App/ ? The path to the precompiled header file is specified by the "Prefix Header" build setting for your target.