I found a bug that creates a 404 page not found error when you try to visit your wordpress site. This is caused by a server which has the default document (index.php) starting with a capital, like mine.
This means that a 404 error occurs when the default page set on the server is 'Index.php' instead of 'index.php'.
I found this line of code in wp-blog-header.php:
20: (false === strpos( $_SERVER['PATH_INFO'] , 'index.php'))
I was able to fix the problem easily by changing the line as follows:
20: (false === strpos( strtolower( $_SERVER['PATH_INFO'] ), 'index.php'))
Now wordpress can also handle server which have their default document setting starting with a capital :)
Hope this helps