Problems with create[Volatile]Image in JInternalFrame

I'm trying to create an MDI application with custom JInternalFrames, called MapFrames. Each MapFrame needs to have access to either a VolatileImage or just a plain Image for double buffering. Now, the problem is that everytime I call createImage or createVolatileImage, it returns a null pointer. I want the size of the [Volatile]Image to be as close to the same size as the viewable area in the MapFrame as possible, so as to conserve memory. I'm creating the [Volatile]Images in the same step as I'm creating the MapFrame. I'd post code to help explain the problem better, but I'm not at my computer at the moment. Any ideas? Thanks in advance!
Oh, as a side, and very off topic, how do you change UIs on the fly? I'm pretty new to Swing. ^^
[ March 11, 2004: Message edited by: Jeremy Tartaglia ]