Crossdomain.xml, same server but i get 'Rejected' error ...

This morning I wanted to put a project (already hosted on the school server) on my own server. Everything works except when i use WWW, 'Rejected, Because no crossdomain WAS found'. I do not understand, I understand 'crossdomain.xml' was needed only if the scripts try to access a different server. There, my application and my scripts are in the same place, I would understand where the problem can come ... any help will be welcome, I'm French, so you can make some efforts for the explanations :)