Ubuntu – NFS4 client within OpenVZ container running Ubuntu 11.10

I have an Ubuntu 11.10 VPS running inside OPenVZ with a hosting company. I'm trying to get it to mount a remote NFS server using NFS4, but can only get it working using version 3. I've been Googling around this quite a lot and occasionally I'll read something along of the lines of "NFS4 clients can't work inside OpenVZ containers". I can't find an up-to-date concrete answer to this so I'll ask here:

Is this true, and if so, great – then I can stop trying to get this to work! But if it IS possible, why's it not working?? Here's what I've done —

• nfs-common installed on client, nfs-kernel-server installed on server
• saw some instructions to install nfs-utils on client, but apt-get can't find the package
• mount from client to server works successfully with NFS vers 3
• server seems to be working fine; can mount successfully using NFSv4 from an Ubuntu VM running on my desktop
• BUT on the successful client machine nfs AND nfs4 is listed in /proc/filesystems, on the problematic one it's only nfs

• I logged a ticket and the relevant module's now been installed on the VPS node, according to the engineer responsible. He's replied that it should now be working but I think he may have just re-enabled the "standard" NFS module (see above re: cat /proc/filesystems | grep nfs)

  $ sudo mount -v -t nfs4 [SERVER_IP]:/ /NFS-ARCHIVE/
  mount.nfs4: pinging: prog 100003 vers 4 prot tcp port 2049
  mount.nfs4: No such device

  $ sudo mount.nfs [SERVER_IP]:/ /NFS-ARCHIVE/ -w -n -o nfs4
  mount.nfs: Unsupported nfs mount option: nfs4

• I've read that I might need to manually load the module by running modprobe nfs before mounting, but I don't think I can do that on a VPS. sudo modprobe -l on the client returns nothing

Any help much appreciated, especially if you can categorically answer the first question – at least if I know it's impossible I can then move onto setting everything up using vers 3!