doing a post doesn’t seem to show any issues in the back unless it becomes really shaky – which is what seems to have happened here. Only thing I can suggest is the following:
1. Reinstall from scratch BUT back up your DB of posts (will not backup images and files) through PHPmyadmin. There is a tutorial here for this
2. Make sure you have .htaccess (if you use a unix server) in the root as well and ensure its properly configured (i.e with the correct permissions). If not, your root can get visible to the public and someone may tinker with your install.