I don't know IPB, but I know mysql and php.
If the password in this config file was originally encrypted, then chances are it's getting decoded somewhere in the script before being used to connect to mysql. When you created the user in mysql, you should have used the decrypted password.
From a command line on your box, try:
mysql -u rock_ivbd2 -p rockmf_ivbd2
Then enter your real password when prompted.
If that doesn't work, then it's not an issue with IPB or php, you need to get the right username, password, or db name.
Email me if this doesn't help.