I’m running WP 3.5.1 and Social 2.8 and am having a similar problem: scheduled posts broadcast unreliably (read very rarely), while manually broadcasting works fine. Unfortunately, the whole point of Social is so that I don’t have to broadcast manually!
In the log, I’m getting things like
[SOCIAL – 2013-04-03 13:16:36] URL search returned no statuses for post #2575.
Doing it manually, I see
[SOCIAL – 2013-04-03 13:32:59] Running request: Broadcast/action_options
, which is missing from the failed attempts.
Any advice?