I installed the SMF CB Plugin.

Had the same problem with the error message.

Found this solution at http://forum.joomla.org/index.php?topic=50531.msg726705

Edit administrator/components/com_smf/admin.smf.class.php

in function updatePass FROM

---

Code:
$query =
"UPDATE {$jsmfConfig->smf_prefix}members " .
"SET passwd = '".sha1(strtolower($username).$pass)."' " .
"WHERE id = '$smf_id' ";

---

TO

---

Code:
$query =
"UPDATE smf_members " .
"SET passwd = '".sha1(strtolower($username).$pass)."' " .
"WHERE ID_MEMBER = '$smf_id' ";

---

Lot of users have problems with there password, userid just type errors in the username password are common so if problem for user stays.
change the password manual in cb and try to login in with their credentials
to see if it works.
In my case it was always the user 

I implemented this soultion and it worked fine because I received a new password. But when I went in and updated/ changed the password (using community builder profile) I discovered that only the joomla password changed. The one of SMF remained. As a result, when you log in on joomla, your smf is not looged in because its 2 diiferent passwords. And you get an invalid username or password error message.
How can this be solved. I had to load smf seperatley and change the pasword to be in sync.