[Mediawiki-l] When I try to edit a page, it just prompts me a box to download the index.php file

[sindefinir sindefinir]

Hi,

I've extensively googling about this error, without been able to find
anything related but this:
http://www.mediawiki.org/wiki/Project:Support_desk/Sections/PHP#.5BRESOLVED.5D_Bug_with_parameters_through_index.phpthat
neither help me to solve the error.

This happens when I am logged in. I'm using mediawiki 1.14 with apache2 php
module.
If I save the index.php, I can see it is an empty file.

Thanks in advance.