Replication director - full vm restore failing with error code 67

hi experts,

want to know if anyone has come across this 67 error code -- (67) client backup failed to read the file list

other details in our configuration

1. topology used - snapshot - snapmirror- snapvalut

2. Backups went fine for volume and VM level

3. Current restoration source is 1st copy (snapshot) so we couldnt gather much of info from NBUplugin logs or trace logs

4. Checked logs from symantec and yet couldnt find any clues on the failure

5. My ESX's are using NFS data stores 

I am expecting some connectivity issue for doing the restore, however couldnt find the stopper here.  Please assist

thanks