500 Internal Server Error with Joomla 1.6

Hello everyone!

After the installation reports that it has successfully installed HikaShop, I click on HikaShop in the backend and get a 500 error. The frontend works fine, but it reports that there are no products, because there are none.

I have tried the FTP installation. I have installed it multiple times. I have deleted all associated tables with phpmyadmin.

I used the very same installer to install it on a different instance of Joomla 1.6 on the same server and it works perfectly. That makes me think that it is not a problem with the installer or the server itself.

I was hoping someone here could help me figure out what it causing it to be broken on my site. I really do not want to rebuild my site if I don't have to. We have a lot of content.

Our website is Joomla! 1.6.3 with Gantry template for frontend, rt_missioncontrol admin template, akeeba, extplorer, hikashop, jce, yvcomment.

The server is Ubuntu 10.10 with LAMPP. I don't think it is the server since I was able to run hikashop on this server with a different instance of J1.6.

Thanks for your time, I will answer any questions as best I can.

Thanks,
Derrick

Thanks for your reply! I looked at the logs and found this:
[03-Jun-2011 16:05:22] PHP Fatal error: Call to a member function setClass() on a non-object in /opt/lampp/htdocs/joomla/administrator/templates/rt_missioncontrol_j16/lib/toolbar.php on line 228

So, I changed my admin template back to Bluestork and HikaShop works fine. I am not a coder, so I don't know what it means. I am going to post with RocketTheme, maybe they can fix it.

Thanks again for your help!