This message generally indicates a permissions problem. Perhaps a directory or file permission was changed while the client kept the file open. Perhaps the file system's share or netgroup permissions changed. If the server were down or the network overloaded, the NFS server not responding message would appear instead.
Log in to the NFS server and check the permissions of directories leading to the file. Make certain that the file system is shared with (exported to) the client experiencing an NFS read failure.
For more information, see the chapter on NFS troubleshooting in the System Administration Guide, Volume 3.