The directory containing the Flash Builder project is not trusted. Normally Flash Builder adds a project directory to a list of trusted Flash Player directories. The problem may be solved by shutdown down all Flash Player instances and trying again. If not, you can add the project location to the trust file yourself.
See the section titled "The User Flash Player Trust directory" in this link: http://www.adobe.com/livedocs/flash/9.0/main/wwhelp/wwhimpl/common/html/wwhelp.htm?context =LiveDocs_Parts&file=00000349.html
Thanks for your reply.
I can see 2 files in this folder flashbuilder_plugin.cfg and flashbuilder_plugin.fbr.
Could you please let me know how I can configure these files? I cant see from the document you given.
Edit flashbuilder_plugin.cfg in a text editor. You will see a list of directories. Add the directory you had a security error on to the list. Shutdown all flash instances and try again.