Fatal error: Call to a member function addFieldToFilter() on a non-object in magento

Have you upgraded your magento version OR installed any module/extension manually?
If you getting this error: “Fatal error: Call to a member function addFieldToFilter() on a non-object ……” after doing any step above then you have to following steps to solve:

Step 1: Re-index the all tables.
a) To re-index Go to your site admin panel.
b) System > Index Management
c) Select all rows and submit button with reindex selection in dropdown.

Step 2: Clear all cache and session.
a) To clear all cache and session Go to your site admin panel.
b) System > Cache Management
c) Select all rows and submit button with select ‘refresh’ option in dropdown.
d) Also press ‘Flush Magento Cache’ button.

It will work for you.