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Quite regularly I find that Eclipse Juno (4.2) on a Mac Book Pro will fail to start - getting stuck at the "loading workbench" message.

This is how I fix it:

Force Quit Eclipse

$ cd $(WORKBENCH)/.metadata
$ rm .lock
$ mv .plugins/org.eclipse.core.resources .plugins/org.eclipse.core.resources.bak
$ open -a Eclipse --args -clean -refresh

Eclipse should start but with no projects. Close any open files, and then exit Eclipse.

$ rm -rf .plugins/org.eclipse.core.resources
$ mv .plugins/org.eclipse.core.resources.bak .plugins/org.eclipse.core.resources
$ open -a Eclipse --args -clean -refresh

Eclipse should start with all your resources back.

Eclipse:fails to start is mentioned on: Eclipse