Gatekeeper reports that the AIR package is damaged

We develop an AIR application which runs both on Windows & Mac.

Distribution is done using a signed AIR package.

Installer can be downloaded from www.genomecompiler.com

Since Apple released Mountain Lion, gatekeeper prevents our installer from running and we must instruct our users to change their security settings - Allow applications downloaded from anywhere.

Additional information from apple: http://support.apple.com/kb/HT5290

I purchased an apple developer license and should have all the information needed.

What should I do in order to sign an AIR package using an apple developer ID?

Thanks,

Roy