Problem: 500 internal server error

We have a strange problem with our server. Normally we use our server (Linux/Apache with WHM/cPanel) for hosting client websites. All the websites we build are Joomla 1.5, and there has never been a problem. But now we have tried to install two new CMS on newly created accounts: Joomla 2.5 and Wordpress 3.3.1. On both these newer versions, our server gives out a "500 Internal Server Error" instead of installation steps. Still no problem with Joomla 1.5, only problem with 2.5 and Wordpress. You can see the two errors here: Wordpress -> [login to view URL]~wpnettpa/ Joomla -> [login to view URL]~joomlate/ Both these links have fresh installation-packages from Joomla and Wordpress. We have been told from a Joomla-expert that the problem is most likely small and easy to fix, either due to scriptproblem or missing something on the server. We need someone to fix this problem quickly! Please write 500SERVER in the bidding title, to show that you have read and understand our problem.