olly - 7:14 pm on Jun 9, 2010 (gmt 0)
Are you sure you kept the same titles, meta tags, h1, h2, etc ? Absolutely no modification on these elements ?
I have just investigated and I see that h1 tags have been changed - there were previously 5 <h1> tags on the homepage and now there is just one <h1> tag with different text. Everything else is as it was before. Could something this minor have caused this?
Did you accidentally leave sitewide noindex/nofollow robots meta tags in place? I've seen that happen before when having a development version of a site go live.
I cannot see the presence of any robots meta tags..