Bug after installing Joomla

Hi, I tried to install Joomla (fresh installs of 1.7 and 1.6.6) through Simplescript and in a second attempt manually. At first it looked OK but when I wanted to edit an article in the back-end I get empty pages or ages without css loaded. Actually the page source code started with <script> in stead of <html>… I have checked it with Firefox and Chrome (OSX and windows machines) and the situation reproduces each time. I have installed many Joomla sites before but have not seen this before.

Any suggestions how to solve this?

Best, Ruud

Does anyone know how to solve it?