I created a very simple test application in 2.5.5.1, containing 1 entity and 2 forms (overview and newedit). When i'm running the application without security enabled the applications works fine in both firefox and ie. But wheb i set the security on production the application will not run in firefox. It looks like it refreshes every second before even showing the login form. The application works perfect in IE! I'm using the default theme created by mendix.