..... as soon as the site reaches a certain level of traffic, the search facility goes offline in an effort to keep the boards running otherwise everything becomes so slow it starts to grind to a halt.
The number of guests grows all the time and therefore the site gets busier all the time - Pete made an announcement recently that he will be switching to a server with greater capacity - and we should hopefully have Search working far more often if not consistently !
The only time I get to use search successfully is in the morning, before the US wakes up!!