Getting Internal server error when adding or deleting pages

Last week I had no problem adding new pages and now everytime I try to add a page or delete a page I get an internal server error. I have made no changes and haven’t a clue what is going on. My site is securityproductsmall.com and it is hosted at GoDaddy. I called them and they said there was nothing wrong with anything on their end and suggested I install WP Supercache plugin, “which I did,” and if that didn’t work try to reindex the tables on the database. The problem is I am a newbie when it comes to this kind of stuff and haven’t a clue where to begin. I have phpmyadmin on my server but have no idea where to go to reindex or anything. I have tried searching on this topic, but have come up empty handed on anything I can even begin to understand. I was wondering if anyone could help with this or might have an idea if this could be because of something else?