Fatal error

[Ahmedtanveer]

Fatal error: Call to a member function isLockExists() on a non-object in /home4/ahmed/public_html/app/code/core/Mage/Index/Model/Lock.php on line 257

How to solve this ? 

[Mukesh Tiwari]

Clear caches and clear  magento/var/locks enteries and then check.

Have you upgraded your magento?

[Ahmedtanveer]

Through file zila ftp i went to publichtml/var/cache deleted all the files in this directory. Nothing happened and the error is there. Please guide me through the steps ? I must be doing some thing worng.  

I was installing magento for the first time so it's not an upgrade it's a new installation. 

Please help me through this. 

Much appriciated. 

[Ahmedtanveer]

I didn't install the sample data so does it has some thing to do with the that ? I just downloaded the full release version 1.9.1.1