VerifyError: Error #1053: Illegal override of concurrency in mx.rpc.http.mxml.HTTPService.
It looks like the same error as the one described in:
Steps to reproduce:
This occurs after I download as3corelib.swc 0.93 and put in my Flex project's libs folder. Inside my app, there is an mx:HttpService.
It looks like some sdk incompatibility.
Instead of putting downloaded as3corelib.swc into libs folder. Copy and paste as3corelib source code into your own project. You can download the source code by using svn from http://as3corelib.googlecode.com/svn/trunk/
For example, I only use JSON library. So I just need to copy com.adobe.serialization.json folder to my project.