Look at it in edit view. Is it right? If so, you've probably got something it thinks is markup somewhere and it's trying to parse it as such.
I thought that might be the case at first, but one of the things I did was copy the text from the edit word for word completely and posted it in the new post. No problems on the new post.
It may be an issue with the fact that I was doing it from work. >_> Today was the first time that happened though. I guess I'll hold off on editing for a bit until I have something non-cosmetic.