CMS windows gives me a white screen

I am using a Beagle Bone Black with ubuntu installed on it for my server. I was able to get the CMS installed correctly, but right after I tried to log in, the screen stays white (Firefox). In IE, it gives me an HTTP 500 internal server error. Restarting the apache server does nothing.

The reason I went with the ubuntu server, was that my other PC (Vista) had problems when I tried to add an android client which kept shutting down the apache server.

The server itself is running since I am able to see the "info.php" screen. Since everything else had mostly worked before, I am not sure where to even look or what info is relevant.