SharePoint 2010 : access denied on javascript

I experienced similar problems and despite having AAM setup correctly as per the above posts and the solutions guide, the problem was related to the use of non-standard ports for HTTP and HTTPS. I didn't get to the bottom of the problem but was able to switch to 80 and 443 anyway. A word of warning to those grappling with AAM's try reverting to the standard ports if possible.