After researching Application Domains, I understand now that this is not a bug.
The following post by Roger Gonzalez really helped to explain what I was doing wrong: http://blogs.adobe.com/rgonzalez/2006/06/applicationdomain.html Using the following code is NOT recommended: Info.load( ApplicationDomain.currentDomain ); This places the Module's "factory" class definition in the SAME app domain as Flex. You cannot remove it once its loaded unless you shut down your main Flex application. The reason I was confused is because I misunderstood the difference between the above code and this code: Info.load( new ApplicationDomain( ApplicationDomain.currentDomain ) ); which is eqivalent to (see mx.modules.ModuleManager line 459): Info.load(); By creating a "new" app domain, the "factory" class definition is now separated from the main Flex app domain. This new domain is a "child" underneath the Flex app domain. When the Module (TestModule) is unloaded, I believe it causes the "child" app domain to go out of scope allowing it to also be GC'd. Gaurav: Thanks for testing this and helping me. I really appreciate it.
