You should check the logfile (in some cases /var/log/syslog or /var/log/messages if not specified). You can set it with this parameter in /etc/vsftpd.conf:
Don't forget to restart the service, try again and check the logfile for entries.
In most cases it is a permission problem in a parent directory that the user can not enter this directory. I just see "/var/www" in your post and it is possible that you missed the "x" flag for some folder permissions. If they are owned by an other user and/or group, you probably need to set it to "others".
Furthermore you should check the file /etc/shells. It should contain the users shell for logging in. This mistake is done very often that a user is added with /bin/false but the shell is not allowed in this file so you get logged out with an error.
Last but not least: Try to run the service without 'chroot_local_user=YES' to check if it is a login or permission problem.
But first of all: check your logs to find a hint. They should provide something to you.