I think there is a bug, but I could manage it, after suffering sometime, that I want to share with you.
If you get a blank wiki page while editing it in full wysiwyg mode you have to check
Inline Wysiwyg editor
That is inside CONTROL PANELS > WYSIWYG
There is a warning telling us that it is experimental, but, without this you get a blank page.
I got so glad when I discovered it that I had to share here, because someone may have the same issue.