Google punishing sex pages?

[avert]

I work for a charity website - avert.org We're a leading provider
of AIDS information, sex education and sexual health advice and get
around 600,000 page views per week. One of our pages sfeel2
comes top in google for the search terms 'sexual intercourse' and
'having sex'.

Between 28th and 30th April we lost loads of traffic on one of our
most popular pages sfeel1.

We found we lost around 85% of google traffic - 23,000 page views a
week to 3,500.

Previously this page generally ranked 1st on 'questions about sex',
'sex questions' and third on 'sexual intercourse'. After the end of
April it is not even in the top 100. The traffic it now gets comes
only from obscure keywords like 'sex q and a'.

We made no big changes to the page before the drop. The page still has
a high page rank.

Any suggestions for why this happened - and what we might be able to
do about it - would be very welcome. In particular, does anyone know
if google has changed the way it handles queries related to sex?

Mark Kirby - Avert.org