Error establishing a database connection message after making a post

Dear All,

First of all i want to wish all of you a Merry Xmas and a Happy New Year 2007.

I am facing the some problems recently on the items as below:

1) Everytime after i make a post, after the post i recieve a message to ask me to download a post.php message. And when i refresh my browser with my domain name, it will bounch out a message as below:

>>>>WordPress
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 localhost. This could mean your host’s database server is down.

* 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?

If you’re unsure what these terms mean you should probably contact your host. If you still need help you can always visit the WordPress Support Forums.<<<<<

2) But when i check later the posting is in?? Any error on my set-up in the wordpress.

Please help me guys. Thanks in advance.

cheers,
flwong