Thanks for the reply, Alex.
I just checked the debug output - 30 minutes has passed and nothing has happened:
# Social Debug
Current Time: 2012-11-30 00:26:52
## Software Versions
## Social options
social_unlocked: Doesn't Exist
social_last_lock_time: 2012-11-29 23:49:42
The site has no other plugins running. I'll check with my host if SSH access is possible.
[Edit]: I have also turned on error logging, and will get back with the output when I wake up tomorrow :) letting it run a few hours will probably generate more useful information.