I’m upgrading my app and when I try to submit I get the message “This bundle is invalid. Apple is not currently accepting applications built with this version of the SDK, Xcode”

This is a screenshot from my app. If you need more data about my system or app configuration, just let me know.
Thanks
UPDATE
XCode version: 4.2 – Build 4D177b
Ok to turn my comment into an Answer:
You will have to upgrade your XCode installation. The current release versions are 4D502 (Lion) and 4C199 (Snow Leopard). Also the “b” at your XCode version indicates that you are using still a beta release which are generally not accepted for app submission.
If the AppStore insist that you have the latest version go to your “Applications” folder
and delete the “XCode Installer.app“. Then you can download it again from the AppStore.
It probably would also do no harm if you’d removed your installation entirely, therefore go to a terminal and navigate to your XCode directory (usually /Developer) and enter
Then download a fresh installer from the AppStore and you should be fine.