Debugging Java 1.4 API with JSwat?

Hi,
I've got a Swing application that makes heavy use of new 1.4 classes, 
and a nasty bug where a private variable that is only ever assigned to 
in the constructor is somehow re-setting itself to null at some point. 
When I load it into JSwat for debugging, it runs very slowly. Very, 
very, very slowly..

 Also, when I click on a thread, I get "(bad thread state)" in the 
Methods and Locals panels.

I gather from the FAQ that these sorts of problems are caused by use of 
the HotSpot VM. Unfortunately, Java 1.4 no longer includes the classic VM.

Are there any options I'm missing that'll allow me to debug with 1.4?

Thanks,
-Paul