Question: I'm running into a problem submitting my application through the Application Loader. I'm receiving the message "This bundle is invalid. Apple is not currently accepting applications built with this version of the SDK." 

I've installed Xcode 4.0.1 w/SDK 4.3 ("4A1006", March 24), and I've reinstalled both MonoDevelop and MonoTouch. I've also made sure my build/bundle settings are using SDK 4.3, and I've tried each of the min versions of 4.0, 4.1, 4.2, and 4.3.

Suggestions?

Update: I've uninstalled Xcode 4 (rebooted), installed latest Xcode 3 same w/SDK (rebooted), and reinstalled MonoDevelop & MonoTouch. Still no luck unfortunately. I tried with and without manually specifying DTXcode:0400.

I've been reinstalling MonoTouch by re-running the installer. Is there a way to do a clean uninstall of MT and could that help in this case?

Answer: 
Apple changed the keys required in the application manifest in iOS SDK 4.3.1. We've released a new MonoDevelop build to track this.
i had this problem for one week and i just solve it today , it seems that SDK 4.3 has a problem with the monotouch anyway
the one works with me i uninstall the SDK and install SDK 4.2 with Xcode 3.2.5 and Remove monorouch 3.2.6 and install 3.2.3 . and it will work.