override the init and launch methods in your controllers, and the launch statement in your application, and then try putting some console.log statements into your code.
when you start the app in the simulator / on your device you should be able to see these executing.
might help you track down where your issues are happening.
I also had this white screen problem. Does anyone here already had a solution to this issue? I had published an app in appstore before using sencha touch 2.0 and was working fine.
Couldn't advise anyone strongly enough to go down this route. Packaging is an area where you need a responsive piece of software - issues can be introduced at such short notice (see localstorage issues last year) and phonegap/cordova gets fixes out very quickly. Sencha........... not so much.