"Locked" controller head during replication.

In our environment, we have a clustered 7310 replicating to a 7310 with a single controller.  Recently, at or near the end of one of the hourly replication cycles, the primary head in the clustered unit (the replication source) "locked up".  We could not access it with the BUI, our vSphere hosts lost connection to the storage, all of our ~110 vm's in the environment either panic'd or were unresponsive...it was a real mess.
On the replication source, there was a log message at the start of the replication but none at completion.  On the replication target, there were log messages at the start and end of the replication.