I can see all Admin stuff, but not the front page or other pages?

First I tried to simply move WP from a sub-directory to the root directory. That attempt made everything inaccessible.

I tried upgrading from 2.8 to 2.8.2 to see if that solved the problem. Now I’m able to at least access all the Admin area. I see the posts, the comments, etc.

But visitors still can’t see the web page, and when I select “visit site”, I see “under construction”? When I go to the posts, and click “view”, I get a “HTTP 500 website cannot display the page”

Please help. I hope it’s not too complicated.