This is a very broad problem, of which I have no indications to what exactly is going wrong.
I recently updated my app using FB 4.5 and AIR 2.6 using the SDK 1.1.0 and the result is odd. The app when unsigned works fine on both the Simulator and my actual device...however once I sign it, when you start the app, it only shows the splash screen and then the screen goes blank with the background color of the app.
Debugging doesn't prove/disprove anything because as I mentioned when its unsigned it works fine...however once signed it doesn't work at all.
Alright. so After some confusion and frustration....I discovered that when I imported my projects into FB 4.5 from Burrito, that for some odd reason my settings for the app build paths and libraries were all different and these issues caused the failure