Had there been a security issue, there would have been Security Error.
You are getting an IOError, this is because you are calling swf from wrong location(though it is redirected to the content location but flash is very specific about domain names.)
This has nothing to do with Security.allowDomain("*"); - this line is written into the swf for it to be accessed from anywhere.
Your question is not very clear. As far as I understand, the solution is to call the swf from actual content location and to make it accessible there are two options:
- wrtie Security.allowDomain("*"; in you swf file if you are the author.
- put crossdomain.xml at actual location from where you are trying to load the swf.