Recently, after a series of server reboots, one of our server stopped replicating data from primary. Everything in logs looks ok, except that it stalled in the "replset syncing to ..." phase after startup. Restarting either primary or secondary didn't help. I think that the simplest solution would be resyncing from scratch, but the database is large enough and write volume is intensive enough for full replication to take about 16-20 hours that we prefer not to spend right now.
MMS links follow.
Secondary in question: https://mms.10gen.com/host/detail/cfa77b8ec3d9ab5870a3a6892c43ba8f
Its primary: https://mms.10gen.com/host/detail/c070029ad468a0141a72471130b108df