navigateToURL security problem

My flash file accesses some local files… So I set Local Playback Security to Access Local Files Only…

Also I added a navigateToURL(new URLRequest(“http://www.somedomain.com/"),"_blank”) to a button, but when I click the button, It shows the security message “…stopped a potentially unsafe operation…”

Anyway this is working when I host it. But it won’t work locally

(I am using an external preloader)…