I discovered a conflict with 'BuddyPress Activity Plus' - which adds an eEmbed interface for posting links, images and videos within the BuddyPress activity stream.
With 'Social' activated the 'preview' function within the BPAP interface fails to trigger - it's still possible to just enter a youtube URL or static page URL and press enter, whereupon the function detects the link and posts correctly into the activity stream.
However since this is a BP community I cannot expect users to figure out ways around the error for themselves.
How would I go about untangling these two plugins - I can't see anything obvious in firebug, so the only solution I can think of would be hacking the 'Social' plugin to only load on blog pages.
p.s. I am running the latest WP3.21 multisite with BP1.29 and a theme developed from bpdefault. You can view the problem on the Activity page within http://skiddnet.com
Thanks for your help