urgent: system settings

Hi,

I have applied the installation steps in following URL:

http://docs.elgg.org/wiki/Installation

Now I am in Step 4 where I got a page of "System Settings" and after I finished and click saved button. I got an error page of "HTTP Error 500 Internal server error ..."   Can anyone please help me so that I can finish my installation properly? Appreciated for your help.

Regards,