I just searched the phpBB.com support forums and it is a problem with phpBB. According to this topic: http://www.phpbb.com/community/viewtopic.php?f=46&t=1531095&p=9140315&hilit=search+exact+phrase&sid=dec25bccc6d6f942fd29184ec2627010#p9140315 phpBB's "Native search" only i...

It is just the indexing thing but your forum indexes way too much. I was having trouble changing the color of the text in a text box so i searched the help forum for 'text color' and both of those words word ignored. So I tried "text color", actually putting it in quotes but it still said ...