[ALUG] Evolution

As some of you may have noticed, wordwrap in my copy of evolution seems to have become broken. If I just simply type a reply then it stays on a single line to a seemingly unlimited width. But only it seems when I reply to a message. Googled about and looked in all the preferences I can find, but I can't see anything that sets a fixed column width in the composer. It was fine until tonight and I haven't applied any updates or deliberately changed anything for a number of weeks now. Any ideas ?