This search does not seem to work with older threads (that is, before the forum upgrade).
It seems to only work for messages posted recently.
For example, if you go to google and search for an entire sentence which exists inside a new message, the result will be listed in the search.
But if you search for a sentence which exists inside an old twisty-forum message, it will not be found.
I hope there is a way around this, because it could make searching extremely efficient by using the google menu.