Error establishing a database connection

Hi everyone, i know this question has appeared in the forums already, and ive searched through them all, but they have not been able to solve my problem still…

I’ve been using wordpress without problems for a few months. About two weeks ago now, i was visiting the blog homepage, and it came up with an error…”Error establishing a database connection” Prior to this, i did not make any changes to the blog, i didnt even view it, as it happened literally overnight.

I have contacted my host, and he has triple checked the MYSQL server, and it is running fine. Ive checked the wp-config.php file, written in everything all over again, deleted the file from the blog, and put in a fresh new copy, still the same thing..

I just wanted to know why this may be happening and how to resolve it?

Thanks for your help in advance.

-Crawf