Stuck on Visual Editor / Cannot Type in Post Editor

Hi All,

For some reason my post editor is stuck on Visual mode and I cannot change to HTML – and secondly, the white box where I am supposed to be typing in does not allow me to click in it and type :L

What can I do to fix this?

(I’ve looked through this thread and haven’t found any solution: http://wordpress.org/support/topic/visual-editor-stuck-in-html-mode-1 )