Sergiu, I haven't managed to find what causes the problem, but I discovered that using the link works fine (in IE7 the link is available only the first time after you clear the cache because it takes longer to load the editor and you give up putting the button on the tool bar) while using the button freezes the editor. Everything is fine in FF, as usual. Any hints? One trace could be that when using the link you don't affect the GWT widget tree. You maximize the container of the content text area which is also the container of the editor (tabs included). When the button is used, you maximize only the rich text editor, without the WYSIWYG/Source tabs. This freezes the editor in IE, but is handled perfectly in FF..
What I find really strange is that the combo boxes from the tool bar (format, font name and font size) can't be opened or focused with the mouse. At first I though that the GWT releases its listeners after coming back from full screen, but that shouldn't block the opening a drop down box..
If I focus the drop down lists using the Tab key, I can change the selection using the arrow keys and this triggers the GWT listeners.
Also, using IE developer tool bar I can't "Select Element by Click" any of the elements that make the editor. It's like there is a transparent panel above the editor, but there isn't any.
Note that there aren't any exceptions thrown. Everything goes well, except that the editor is frozen.