WAL archive messages in streaming standby server's log

For some reason, after testing failover successfully and then failing back to restore the original primary server, my standby server is acting a little strange. I have the following log messages repeating every 5 minutes:

< 2014-05-06 13:41:17.705 EDT <@> % >LOG: restored log file "000000020000000000000046" from archive
< 2014-05-06 13:41:17.709 EDT <@> % >LOG: record with zero length at 0/46000090
< 2014-05-06 13:41:17.710 EDT <@> % >LOG: restarted WAL streaming at 0/46000000 on timeline 2
< 2014-05-06 13:41:17.710 EDT <@> % >LOG: replication terminated by primary server
< 2014-05-06 13:41:17.710 EDT <@> % >DETAIL: End of WAL reached on timeline 2 at 0/46000090.

Note that these are not shown as error messages, but it doesn't appear that WAL processing is continuing as there are at least a dozen newer WAL files from the primary which are not being copied into the standby server's pg_xlog directory. I suspect the problem lies with the the second line indicating a record with zero length, but don't know how to clear this out so it goes away - short of doing a pgbasebackup on the primary and rebuilding the standby from that.

Anyone have any ideas?
Jay