Funcioning site gets Error Establishing Database Connection

Every few days my website example.com stops working and I get the error message: “Error establishing database connection”.

I am using WordPress 2.7.1 (theme blass2) with the database example_wrdp2, user example_wrdp2.

In cPanel I checked :

Check DB ok
Repair DB ok

For troubleshooting I deleted current user example_wrdp2

Then I added new user with same name example_wrdp2 and same password, so I don’t have to change the wp-config.php .

Then I Add User To Database with all privileges

The site works again but the same happens after a few days or weeks.

Looking forward to your suggestions.