Gah! I have the same problem with my forum! It is fine till you try to edit something then it gets squished together!
One of my members said he was able to fix one of his posts by unchecking a 'HTML' box that is right above your post (near the top left of the text box) when you try to edit it. Then it was fine.
You can try that, but hopefully someone will give you a more detailed answer!
Good Luck!