500 Server error

I just moved my wordpress from /web8 to /web16 using copy and past. I also moved to a different database but imported the old one. I hadn’t used the istallation for posts yet because I had just finished setting up the template. Now when I went to post my article It seemed to work but in the homepage the widget for categories and archives pulls up a page that says 500 internal server error. What could be causing this and how do I fix it. Here is a link to the problematic site http://www.motormayhem.net (sorry if this is considered spamming but I am not sure if I am describing the problem correctly) click on the link called BMX Cycle or any of the categories or archives and you will see the error.

Thanks