I think the problem is related to the theme you have inherited. are you using any theme?? ( check your module.gwt.xml)
Also, use firebug to inspect the dialogbox element. The dialog box is right here but the styles are creating issues.
hope this helps.
SCJP 5.0 SCWCD 5.0
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