Help please! about Error establishing a database connection

Hi everyone,

Please help.
Every now and then, when I try to go to my blog, it gives me this error information:

Error establishing a database connection

This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at sabsql.sabfeng.com.

* Are you sure you have the correct username and password?
* Are you sure that you have typed the correct hostname?
* Are you sure that the database server is running?

And after a while, it will be ok. But this error just came every now and then, and recover itself.. Can anyone help me? I can not think of any reason it is like this. Thank you in advance…