During the duration of the APD condition and after, the array still responds to ping and the netcat tests are also successful. There is no evidence to indicate a physical network or a NFS storage array issue. — VMware KB 2076392
For those of you who have been keeping up with VMware, here is a status update on the NFS All Paths Down (APD) condition: it's fixed!
If you are unfamiliar with the vSphere 5.5 Update 1 NFS APD issue, basically some customers (not all, mind you) across different vendors, ran into an error condition where vSphere would report all NFS paths to be down and thus the NFS mount and any VMs or RDMs on it would become inaccessible—even though the paths were perfectly fine.
If you would like to read further, the issue is described in detail in the above VMware KB 2076392.