I’ve been trying to load a local file with some dummy data and hitting a security warning. I was running out of FlexBuilder 3 and trying to read a local file, so wasn’t sure why I was getting a security error.

I’d come across many references to adding a cross domain policy to a web server, but this is the first full explanation of the security sandbox that made sense to me. Following this, I added:

-use-network=false

To the custom compiler line in the project preferences and all is well. Here’s the link with a great explanation:

http://blogs.adobe.com/flexdoc/2008/06/the_security_sandbox_in_flex_b.html