globally-installed GIMP python plugins are not accessible

gimp python plugins installed to /usr/share/gimp/2.0/scripts cannot be called by gimp.

For example, gimp-plugin-registry includes several python plugins which are installed to:
 /usr/share/gimp/2.0/scripts
None of them are visible in GIMP. There is no problem with any of the script-fu plugins.

This affects:
btn4ws.py
contactsheet.py
file-ora.py
cmyk-tiff-2-cmyk-pdf.py
ez-perspective.py
layerfx.py
from the gimp-plugin-registry.

It also affects any other python plugin installed to /usr/share/gimp/2.0/scripts

Workaround: Copy these files to ~/.gimp-2.6/plug-ins and they immediately appear in their corresponding menus.

In HOME python plugins can be copied to "plug-ins" dir instead of "scripts" to make them available. This is not possible at a system level with /usr/share/gimp/2.0/

This is a fresh install of Oneiric in virtualbox. What I have checked:
- python files are executable
- Refresh Scripts... -> no change
- Plug-in browser -> plugins not appearing there
- Copy the python file to ~/.gimp-2.6/scripts -> no change
- Copy the python file to /usr/share/gimp/2.0/plug-ins (create this dir) -> no change

I cannot tell if it worked in previous versions.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: gimp-plugin-registry 3.5.4-1
ProcVersionSignature: Ubuntu 3.0.0-16.28-generic 3.0.17
Uname: Linux 3.0.0-16-generic x86_64
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Thu Feb 23 17:36:29 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
ProcEnviron:
 PATH=(custom, no User Name)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gimp-plugin-registry
UpgradeStatus: No upgrade log present (probably fresh install)