A friend of mine , was trying to install php-nuke on his host server , there was a slight problem in the config.php file that was preventing php to reach-connect to the database .
The problem was the Defined variable of the location/address of the server ,We fixed that & everything went fine until today .
He tried installing a theme which then he was not able to even bring up the main index page up .
After looking at the problem it took me a while to find where php-nuke is actually reading the theme value from .
I Located the Default_theme column in nuke_config table & By changing it Value to Traditional , php-nuke was up and running good .