Hi Steve
There could be a number of reasons why you cannot use rich text when you post on this forum.
Have you recently changed or updated your web browser, or made any changes to the format on your text editor?
You could try posting with rich text disabled and before clicking on 'Save' try enabling rich text from the 'breadcrumb' at the bottom left of the reply box.
If neither of these options work get back to me and we'll have a look at your reply box toolbar