Remote I/O Error during 'ls' -- NFSv4

I am trying to troubleshoot an intermittent issue where running ls on a volume returns a 'Remote I/O error' immediately.

RHEL Release: 6.4 Workstation
Kernel: 2.6.32-358.2.1.el6.x86_64
NFS version: 4.0

Trying to find a list of NFSv4 return codes that would trigger RHEL Workstation to throw this error. Any ideas? A packet trace show many NFS4ERR_NOENT, but that shouldn't be translated as Remote I/O error.

Thanks,

Elliott Ecton
NetApp NAS Engineer