Please help me… Even I’m facing this same issue. I have searched the whole google and this issue has something to do with particular server only
Mybb/phpbb/joomla/wordpress - all other logins are working perfectly fine…so nothing to do with php.ini configuration
Only Gii login is not working.
If I enter wrong password then it shows me error as Invalid Password but on entering correct password it redirects me to the same login page.
One more thing, main login page of yii where we have default login admin/admin or demo/demo is only working if I check Remember Password
If I try to login without checking remember password. It takes me to first tab without logging-in.
Please tell me how to make GII login generator work. Even any hack will be fine… Current hack which thread poster have mentioned is not working
Please let me know which file to make changes so that I’m able to login 
For remember me functionality, I hade to change below line:-
$duration=$this->rememberMe ? 3600*24*30 : 0;
to
$duration=$this->rememberMe ? 3600*24*30 : 3600*24*30;
And then only I was able to login on main yii application. I can do such kind of change in Gii code generator too but which file does Gii code generator uses for login???