3
Check your path again in the mainfile.php
I had this happen once and discovered my host had moved me to a different server. For example:
XOOPS_ROOT_PATH', '/home/mysite/public_html
Became: XOOPS_ROOT_PATH', '/home2/mysite/public_html
My mainfile.php still had the home instead of home2 in the path thus XOOPS was out not in the path anymore.
There are at least three places in the mainfile.php you will have to change this.
Hope this helps!
Quest