Yii Automatic Logout and Session issues

I am working on a PHP script built on Yii Framework,from yesterday i am getting problems with login and sessions.User settings are not saved and user is being redirected to login page automatically.

Error Log says

[:error] [pid 15451] [client 127.0.0.1:41045] PHP

require() /home/public_html/yiiframework/web/CBaseController.php:127, referer: http:/domain.com/merchant/Settings

And the Line 127 is

{

 ob_start();


 ob_implicit_flush(false);

127 require($viewFile);

 return ob_get_clean();


 }


 else


 require($_viewFile_);


 }

you may use it in DEBUG mode, so that you can trace your errors. There would be a chain of events and this is the final error. You can find it out yourself.