I have a site You-Can-Have-It.com with WordPress installed in a /blog sub-directory. It was working just fine until I discovered that some time after the last update the only post viewable is the most recent one. Although all posts can be viewed and edited from within Admin as usual, attempts to view them outside of Admin get the 500 Internal Server error.
I saw that Bulletproof Security plugin was implicated in one other similar problem, but deactivating my plugins and removing the .htaccess files didn't fix it.
I find it strange that I can edit and update a post, save it and then not view it. At least the database is working. Got any ideas? I've already spent half the day on this.
Take a look at http://http://www.you-can-have-it.com/blog