Edit Page error

Hi!

Editing pages in visual mode is suddenly impossible, because the edit vindow itself is only one word wide. My entire page text is displayed in a very narrow, very long column of single words.

Screenshot: http://detjyskevokalensemble.dk/wp-content/uploads/2012/08/Screenshot-17-08-2012-104033.png

Is it a browser issue? Firefox and Chrome both display in this manner. Any thoughts? :-s