Looks like you are using GWT-Ext. Not having worked with GWT-Ext I cannot offer any suggestions for it.
However, you might want to consider GWT LazyPanel or something like a
GlassPanel
I personally would prefer the LazyPanel as the glass panel will block all user interaction with the whole UI.
In future, while posting code, please
UseCodeTags
I have edited out your original post this time. As you can see the code tags make the code much more readable and easy to understand.