I googled the problem and saw alot of recommendations including changing the database user and password and editing it in the configuration.php.
Instead, I decided to contact my host. They requested for my cPanel login details. After some minutes, the problem was resolved and my bulk sms site was restored. When I asked them what went wrong, I was told it was caused by a problem with the MySQL server. .
So, if you experience such problem, try to talk to your host before making changes to your config file.
Have you experienced same? How were you able to resolve it?