Uber_SEO - 3:38 pm on Nov 13, 2012 (gmt 0)
Just thought I'd report back on this, as it may turn out to be useful to someone else. Turned out that the hosting company had rolled out some IP blocking technology to their servers, which had blocked Google from accessing the domains. No idea why they did this, and trying to get to the bottom of it.
Effectively, Google's message in the SERPs was incorrect.