The hosts have said:
The issue seems to be that the /home/vhost/html/libs/mysql.inc.php file is of zero length - I believe this would contain the relevant sql class that is reporting the error.
Upon checking the following additional files are also zero bytes in size.
./images/moods/default_dark/index.html
./images/moods/default/index.html
./images/forumimages/default/index.html
./images/avatars/default/index.html
./sessions/index.html
./sessions/index.htm
./cache/index.html
./cache/index.htm
./libs/mysql.inc.php
./includes/privacy.php
./includes/header-insert.php
./includes/intro_102.php
./includes/index.html
./includes/boardrules.php
./includes/coppainsert.php
./includes/intro_8.php
./templates/compile/index.html
./styles/index.html
