7
The Website is up and running.
The problem was that he has overwritten the "secure.php" file in:
/xoops_data/data
If you have installed XOOPS as a fresh installation of XOOPS 2.5.x, then all the database information is now in the "secure.php" file (previously it was in mainfile.php, but in order to improve security, it has been moved to "secure.php"). Therefore make sure that you don't overwrite that file.
And as always, make a backup before you update it, so you can go back and copy over the "secure.php" file, if needed.