Take the tour ×  I've scoured the questions asked here and
thought I had found an answer earlier with deleting the data for
the simulator, but my issue appears to be slightly different.
When I run the app, which was working on the last version of
xcode and has been run on other systems in the simulator, in the
simulator, it opens up the simulator and the simulator screen is
black. Not the normal black issue that I've seen where it is
black but you can see the iPhone or iPad frame around the edge
still, the whole simulator window is black like it hasn't
loaded.  When I look in the debug log it always says this and
only this "error: failed to attach to process ID 0".  I've tried
the steps located Xcode compiles my App, but can't run it in the
simulator and I've uninstalled and re-installed xcode. The issue
still persists.  If anyone has any ideas would be much
appreciated.  share|improve this question Did you update to
Xcode 4.5.1? I believe it was released yesterday and fixes some
simulator related problems.