If you are gettting this error when installing WordPress MU then make sure that the parent folder doesn’t contain wp-config.php file. Or you can rename it for a minute and then install the MU and rename it back. This problem is bound to occur to persons using shared hosting since the addon/subdomain folder is created within the root folder and if wordpress is installed for root domain then the wp-config.php file exists and which will create the problem.
Also if you get a error like this :-
If your blog does not display, please contact the owner of this site.
If you are the owner of this site please check that MySQL is running properly and all tables are error free.
Database Tables Missing.
Database tables are missing. This means that MySQL is either not running, WPMU was not installed properly, or someone deleted wp_site. You really should look at your database now.
What do I do now?
Read the bug report page. Some of the guidelines there may help you figure out what went wrong.
If you’re still stuck with this message, then check that your database contains the following tables:
If you suspect a problem please report it to the support forums but you must include the information asked for in the WPMU bug reporting guidelines!
then just delete the database table related to this particular install and the corresponding wp-config.php . If you are still unable to solve it contact us and we will solve it for a very nominal price.