I'm having a similar problem as mmoconnor in another thread :
"I can see the content and the html in the edit box before and after I save it (the page). I can go back and edit it again and again. But I cannot get it to appear on the page!"
I am using the default WP 2.3 theme, but did momentarily switch to another theme to take a look at it, then went back to the default theme.
I've tried deleting the page and starting a new page. That didn't solve the problem.
I re-uploaded the wp-page.php file as a possible solution, but that didn't work.