Why is Eclipse p2 refusing to update org.eclipse.equinox.simpleconfigurator?

When I try to update, I get this error:

Cannot complete the install because of a conflicting dependency.
  Software being installed: Eclipse Platform 3.7.2.v20120207-1839-9gF7UHPDFxGjd-PqDr2jX_4yKaumkoHTz04_q-q (org.eclipse.platform.feature.group 3.7.2.v20120207-1839-9gF7UHPDFxGjd-PqDr2jX_4yKaumkoHTz04_q-q)
  Software currently installed: Equinox Core Function 1.0.0.v20110502-7K7VFBVF7RZHQQHxNc02A66 (org.eclipse.equinox.core.feature.feature.group 1.0.0.v20110502-7K7VFBVF7RZHQQHxNc02A66)
  Only one of the following can be installed at once: 
    Simple Configurator 1.0.200.v20110502-1955 (org.eclipse.equinox.simpleconfigurator 1.0.200.v20110502-1955)
    Simple Configurator 1.0.200.v20110815-1438 (org.eclipse.equinox.simpleconfigurator 1.0.200.v20110815-1438)
  Cannot satisfy dependency:
    From: Equinox Core Function 1.0.0.v20110502-7K7VFBVF7RZHQQHxNc02A66 (org.eclipse.equinox.core.feature.feature.group 1.0.0.v20110502-7K7VFBVF7RZHQQHxNc02A66)
    To: org.eclipse.equinox.simpleconfigurator [1.0.200.v20110502-1955]
  Cannot satisfy dependency:
    From: Eclipse Platform 3.7.2.v20120207-1839-9gF7UHPDFxGjd-PqDr2jX_4yKaumkoHTz04_q-q (org.eclipse.platform.feature.group 3.7.2.v20120207-1839-9gF7UHPDFxGjd-PqDr2jX_4yKaumkoHTz04_q-q)
    To: org.eclipse.rcp.feature.group [3.7.2.v20120120-1424-9DB5FmnFq5JCf1UA38R-kz0S0272]
  Cannot satisfy dependency:
    From: Eclipse RCP 3.7.2.v20120120-1424-9DB5FmnFq5JCf1UA38R-kz0S0272 (org.eclipse.rcp.feature.group 3.7.2.v20120120-1424-9DB5FmnFq5JCf1UA38R-kz0S0272)
    To: org.eclipse.equinox.simpleconfigurator [1.0.200.v20110815-1438]

I created the p2 update site by copying the necessary plugins from the ZIP file.

How can I force p2 to update the plugin?

This happens because the org.eclipse.equinox.simpleconfigurator bundle is marked with "singleton=true" in the bundle manifest. This does not allow p2 director to install more than one instance of this bundle.

You could update it:

1. either by uninstalling the original bundle first (which would be not easy since this bundle is part of RCP feature),

2. or (which is probably more pragmatic solution) manually replace the 1.0.200.v20110815-1438 bundle in your p2 repo with the original 1.0.200.v20110502-1955 bundle. Since the versions of the bundles are the same (1.0.200) you may expect that the contents is the same as well.