The IllegalOperationError exception is thrown when a method is not implemented or the implementation doesn't cover the current usage.
Examples of illegal operation error exceptions include:
- A base class, such as DisplayObjectContainer, provides more functionality than a Stage can support(such as masks)
 - Certain accessibility methods are called when the player is compiled without accessibility support
 - The mms.cfg setting prohibits a FileReference action
 - ActionScript tries to run a 
FileReference.browse()call when a browse dialog box is already open - ActionScript tries to use an unsupported protocol for a FileReference object(such as FTP)
 - Authoring-only features are invoked from a run-time player
 - An attempt is made to set the name of a Timeline-placed object