Some users had problem similar to yours… problem was that they used the forum options to change the display name… and then tried to log in with that "display name" instead with the original one that they did register on the yii forum…
I also have the same problem reported by friends. I registered, I have not changed the display name, and I can afimar I clicked on the link for verification of account sent to me by email. But I only have access to the forum, I have access to the site. When I try to log in outside the forum login or password incorrect. On the forum I I can login, but login not persist throughout the site, it is logged only in the forum.
Most users had problem logging because the yii forum allows to log in by using the username or email, but the yii site was working only with the username.
The yii site code has been updated. Now you can log in with the email, too.
The yii site has been updated again and hopefully all the site login problems fixed.
There was a problem with some "special" characters in the password, for example if someone had $ in the password he could log in on the forum, but not on the site. Now the code has been adjusted to process the login credentials the same way.