Erro ao usar update do Eclipse

Não estou conseguindo usar o update do Eclipse para instalar ou atualizar o Eclipse e os plugins.

Erros do tipo aparecem quando tento usar os update sites:

An error occurred while collecting items to be installed
No repository found containing: org.eclipse.datatools.enablement.jdt.feature/org.eclipse.update.feature/1.6.0.v200804021-1-07w311916263466
No repository found containing: org.eclipse.datatools.enablement.msft.feature/org.eclipse.update.feature/1.6.0.v200804021-441_kE77c7QARCMOS
No repository found containing: org.eclipse.datatools.enablement.msft.sqlserver.ui/osgi.bundle/1.0.0.v200805160737

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An error occurred while collecting items to be installed
No repository found containing: org.eclipse.datatools.enablement.msft.feature/org.eclipse.update.feature/1.6.0.v200804021-441_kE77c7QARCMOS
No repository found containing: org.eclipse.datatools.enablement.msft.sqlserver/osgi.bundle/1.0.1.v200805152355
No repository found containing: org.eclipse.datatools.enablement.msft.sqlserver.ui/osgi.bundle/1.0.0.v200805160737
No repository found containing: org.eclipse.datatools.enablement.mysql.feature/org.eclipse.update.feature/1.6.0.v200804021-441_kE77c7QASCMPN
No repository found containing: org.eclipse.datatools.enablement.oda.designer.feature/org.eclipse.update.feature/1.6.0.v200804021-21-8s733I3C7F4K63
No repository found containing: org.eclipse.datatools.enablement.oda.ws.ui/osgi.bundle/1.1.0.v200805261930
No repository found containing: org.eclipse.datatools.enablement.oda.xml.ui/osgi.bundle/1.1.0.v200805270900