llegalArgumentException: adding a window to a container

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: adding a window to a container

at java.awt.Container.addImpl(Container.java:1010)

I am using NetBeans to create my app... I have a seperate class that creates a Frame and I would like to be able to call this class to generate a frame and add it to an internal frame in the main class. Is this possible? Thanks.

[404 byte] By [Jensenryaa] at [2007-11-27 3:09:44]