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