In your description at [link|http://z.iwethey.org/forums/render/content/show?contentid=157019|http://z.iwethey.org...?contentid=157019] it said 15% of CPU time was spent on this query. I've been working from the assumption that this was the problem that needed solving.
If that is wrong, then reasonable theories to explain what didn't happen are, of course, superfluous.
Cheers,
Ben