Hmmmm. Can you post your code? I've used modal=true many times an it certainly renders other frames useless (well, okay, so I can move them around under Linux, but I can't bring them to the front or enter anything in them).
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com
subject: public Dialog(Frame owner, boolean modal) not working as expected