Thank you very much for the help here! I cant explain the problem, but the solution have been:
Have seperate users for the database and restart!
Of some reason it helped when I created a new user!
I found that, because of some mistake when editing some of the mysql*.cf files I removed the user line! and then the /var/log/mail.log told me that it was the wrong username and password?!
And now my mail server works! thank you for the help!
NOTE! The user for the database I first used worked well and is still in use now, just only for pureftpd-mysql!