have the same problem since updated from 4.1 to 5.0
during high load times (backup) we get the same "latency" messages.
We allready use the software iscsi adapter with broadcom nics. all cables seem to be ok (cat6).
We get this messages every night, wenn vmware data recovery does its backups. once 2 of 4 path went down on one of 4 hosts...