"CodeSign build/Release-iphoneos" error prevents Packaging for Ad hoc or iTunes Store

I am having problems Packaging my app for iOS Ad hoc (or even iTunes Store). At compilation stage I get this error in Titanium Studio:

[ERROR] ** BUILD FAILED **
[ERROR] The following build commands failed:
[ERROR]         CodeSign build/Release-iphoneos/MyApp.app
[ERROR] (1 failure)

I have tried killing off all my keys and certificates and re-generating a Production Certificate and Ad hoc Provisioning Profile, but I get the same error.

I am running the most recent version of Studio and using the iOS 6.1 SDK.

It looks like the problem I am having has been reported before - has it been fixed? https://jira.appcelerator.org/browse/TIMOB-13640?page=com.googlecode.jira-suite-utilities:transitions-summary-tabpanel

This is really critical for us, so any help very much appreciated!

Thank you for your attention

Caroline