GWT DialogBox - sizing problem when animation is enabled

Question

GWT client code:

DialogBox dialog = new DialogBox();
dialog.setAnimationEnabled(true);
SimplePanel panel = new SimplePanel();
panel.setPixelSize(800, 600);
dialog.setWidget(panel);
dialog.center();

with the above code the width of the dialog is not set properly - the dialog is cut off at about 400 px.

Without animation enabled it works ok, like in the code fragment below:

DialogBox dialog = new DialogBox();
SimplePanel panel = new SimplePanel();
panel.setPixelSize(800, 600);
dialog.setWidget(panel);
dialog.center();

GWT ver 2.04
Firefox: 3.6.9
Chrome: 6.0.472.55 beta

Any ideas what the problem might be?