When i selected the posts/ comments tab from the back office it always gave me error : unknown filterset[].
I read through the comments and did some thing

I quoted out around line 682
default:
// Delete the pref_browse_tab setting so that the default
// (full) gets used the next time the user wants to browse
// a blog and we don't run into the same error again.
//$UserSettings->delete( 'pref_browse_tab' );
//$UserSettings->dbupdate();
//debug_die( 'Unknown filterset ['.$tab.']' );
break; // added by me

This fixed the problem for me. Not sure if I did anything wrong. but it seems working.