Thread:Project:Support desk/Fatal error: Call to a member function addWikiMsg() on a non-object in /home/username/public html/wiki/includes/specials/SpecialLinkSearch.php on line 82/reply (4)

Note, BOM's cause a different type of error. (headers already sent error)

This type of error would be caused if the relavent OutputPage wasn't being returned properly from the SpecialPage's context. I have no idea how that can happen (and furthermore, no idea how that could happen without many other massive errors popping up everywhere on your wiki) [This is probably a bug in MediaWiki]

Could you test temporarily disabling all extensions (just comment out the require_once lines near the bottom of LocalSettings.php) just to check if its being caused by one of those extensions (seems unlikely, but good to check).

p.s. You may want to change the value of $wgSecretKey and $wgUpgradeKey afterwards since they were left in your LocalSettings.php