upgrade has caused page content to disappear

If content displays within WordPress itself when you are logged into the dashboard but does not display on the front end of your site it is almost always a theme problem. If you have access to server logs, such as error logs in cPanel, you can see what errors are being thrown up.

The easy way to test if the theme is the problem is to change your theme to the default TwentyTen theme and see if your content appears.