iPhone simulator just shows blank grey screen?

I'm trying to learn iOS development, and have run into a problem that has stopped any and all progress. Whenever I build and run my code on the simulator, I just get a blank grey screen! I can't find any help on the subject, so I turn to you wonderful people here. I have no idea what's wrong. Even when I start 开发者_JS百科a new blank project and build/run it, I get a blank grey screen. It seems like something is wrong in xcode that's preventing my MainWindow.xib file to be used.

Like I said, I'm just learning, so I don't have much experience as to how this all works.

Try this: with iOS Simulator active, select Window->Scale->50%. This worked for me after frustrating hours and hours of restarting the computer, reinstalling Xcode, and searching the Web. Turned out there was nothing wrong with iOS Simulator, just that the default Scale of 100% hid all the icons. OS X 10.9.3, Xcode 5.1.1, iOS Simulator 7.1.

Some of the sample project templates (e.g. 'view based application') don't show anything interesting - only a grey screen (bceause it's up to you to actually add something to the view). But if you create a new "Navigation based application" sample project, you'll see a blue nav bar and an empty table in your app.