Sandbox violation message

This is kind of a strange one…
I am trying to run my local flash movie (which reads from an image folder on my server). My main movie calls another swf which is also on my server. When I try to run the main movie, I get:

*** Security Sandbox Violation ***
SecurityDomain ‘http://mydomain/called.swf’ tried to access incompatible context ‘file:///C|/Documents%20and%20Settings/Me/Desktop/mainmovie.swf’

Any ideas what this means?