Too long loading locks document in non-edit mode in Firefox

When opening an existing document for edit in wysiwyg, if the document takes too long to load and user clicks in the rich text area before the document has loaded, then the document remains non editable.
To reproduce:

• create a big document (large images, etc) -> clear browser cache, to be sure it takes long to load
• open it for edit in wysiwyg
• click the RTA as soon as possible (when the doc inside is loading).
  Now you won't be able to edit it even after the document has finished loading.
• Click outside the RTA then inside again
  Now you'll be able to edit the document.

It seems to be because GWT turns the document in edit mode after the doc is load, onFocus() on the richtext area. Since in the situation above you take focus before the document is load, onFocus() is called only when you click out then back in again.