A while back I created several page layouts for my company so that we would have a standard format for pages, news stories, etc. We really hadn't had any problems until one of our news stories had a '+' in it's title, and thus the suggested filename had a '+' in it. Apparently you are allowed to create a page with the special character '+' in it, but it will break your page.
The behavior we saw was that you could see all the page content in edit mode, but none of it would show up when it was checked in/published. Also, there was some odd rendering of the page in edit mode.
I was scratching my head over this for a while and pretty much randomly stumbled onto the solution. In the future, I'd suggest removing any non alpha-numeric characters from file names just to be safe, even though SharePoint doesn't warn you or remove them.