For reference, I originally emailed support direct and their reply was to disable other plugins and check we had the most recent version installed. I haven’t disabled all other plugins yet (will do so when I next work on the project) but here’s a list of plugins we have installed and active:
Twitter Tools
Wordpress SEO
Widget Logic
Contact Form 7
Domain Mapping Plugin
None of these deal with custom post types. We do have custom post types defined through other themes with other child sites in the multisite, but not this particular child site.