WordPress MU

Hi guys, yesterday i've upgraded my dear old MU 2.65 with the MU 2.7, but i have a very strange problem:

in my root server (hostgator) i have an home.php that is my homepage (outside MU), and the index.php of MU.
Home.php is the "priority" page in the htaccess:

DirectoryIndex home.php index.php

So, people that digit: http://wikiroma.it visit my homepage, and clicking http://wikiroma.it/index.php they should go on my MU homepage. It worked really fine with the 2.65, but since i've upgraded to 2.7 the index.php redirects to my home.php.

And so no way to lead users to my MU homepage (community). It is not an .htaccess problem, cause if i upload an empty index.php page it all works and it does not redirects to home. If i reupload the MU index.php it redirects again to home.php

please guys, none can help me? What MU file could make this issue happen?
The only 2.65 old file i've keeped online is the config.php (i'v only addedd the secret api keys), maybe could be the cause of this problem?

Tried renaming home.php to something else? Try home1.php and set DirectoryIndex home1.php index.php
See if this works.