while updating from version 4.1.1 to 4.2
i uploadated 2 folders those are;-

/includes/
/modules/

but then i got an error:-

Fatal error: Cannot redeclare cache_app_cache() (previously declared in /home/krokite/public_html/includes/libs/admin_a.hook.php:11) in /home/krokite/public_html/modules/cache/cache.hook.php on line 12

it got solved by del :-

function cache_app_cache($parr, $page = 1, $client=array()) {
return false;
}

from :-

/modules/cache.hook.php

enjoy !!!
now its fully updated to .. 4.2 \m/
cheers