@egarayblas, do not panic! 
So, the first thing is that I did not have this “exactly” problem you and other guys are having - I mean getting that sinister message about codesign verification.
BUT by the other side, yes, I did have many problems regarding the update of my Xcode for the latest one, principally because I`ve had to renew my Apple Developer membership and so I needed to renew my certificates, provisionings profiles, and so on.
So after I get to renew my membership at all, I went to the mission of upgrade Xcode! Sincerely, by this time, (that all Ansca Staff worked on getting the Corona daily-builds working nice with the latest version of Xcode 4.3.1) it was not a pain! Opposite of it. I went to my Apple Developer Portal, clicked on iOS and found the link saying to upgrade the Xcode SDK. So this link went to Apple Store and direct for the Xcode latest version page. So I clicked INSTALL, it took a long time to download everything (1.6Gb) but after that it did install alone.
And then I made sure that my “old” Xcode was not in my Dock (the icon) and went to my applications folder (because the new Xcode installs itself there and not at the Developers folder anymore) and clicked on the Xcode icon there. After that it starts to install and ask you if you would like it to REMOVE your “older” version of Xcode (eg. 4.2.1), I said YES and it did all the job for me in a short time and so I was able already to open my new Xcode and its Organizer and see that everything was working (including my registered test devices, certificates and profiles).
So, after that I installed the latest daily-build of Corona (exactly the build 766) and went to try to BUILD for iOS. And so I went ahead and saw that CoronaSDK was beautifully “seeing” the new Xcode path and so it was able to build again! 
To summarize: Get the new Xcode at Apple Store, let your older version there where it is right now (just remove the Xcode of the Dock if you keep it there), after the download/installation complete, you click on Xcode and it will get installed seamlessly and even remove your (now) older version of it. Just make sure to have the latests CoronaSDK daily builds and I believe you would be good to keep going.
I hope that helps,
Rodrigo. [import]uid: 89165 topic_id: 22661 reply_id: 93652[/import]