I don't really have a solution, but a suggestion as to why it might be working locally. If you created the project in Flex Builder it will add the source location to a trust file:
Documents and Settings\$UserName$\Application Data\Macromedia\Flash Player\#Security\FlashPlayerTrust\flexbuilder.cfg (for my setup anyway) This will override any sandbox issues when you run locally and possibly hide whatever security issue you're encountering when you deploy.
