只是遇到了同样的问题:重新启动模拟器和Xcode不适合我，而重新启动我的mac却很好!

对我有用的是:

启动“监视器”，杀死gdb-i386-apple-darwin 重启iOS模拟器

固定它! !希望这能帮助一些人避免非常沮丧的几个小时。我用以下方法解决了这个问题:

Clicking on the project name in the left pane (at the very top). This will bring up a new menu to the right, something like the project/ target editors in XCode 3. Click on Build Settings up at the top. Under Packaging make sure your product name is the same for every build, and equal to whatever it says it's attaching to. Eg if XCode is Hanging at "Attaching to myLCBO" but your product name is "LCBO Finder" then it won't build. That was exactly my problem because I renamed my app half way through development.

我的解决方案是纠正笔尖名称。(我之前为iPad版本更改了我的nib名称，但后来我删除了iPad nib文件)。然后它又能正常工作了。

说了这么多，做了这么多。我不得不停止模拟器。然后消息改为下载Mac OS X 10.6核心库。

我尝试了这个页面中的所有方法，对我有效的“新”解决方案是进入模拟器，在iOS模拟器主菜单中“重置内容和设置”。