Opening the "Software Updates" on Eclipse 3.4M6 causes the following Problem when Orbit has been installed (I have been testing it with several versions up to S20080427194908):
An internal error occurred during: "Fetching children of Known Repositories".
org.eclipse.equinox.internal.p2.extensionlocation.ExtensionL ocationMetadataRepositoryFactory cannot be cast to org.eclipse.equinox.internal.provisional.spi.p2.metadata.rep ository.IMetadataRepositoryFactory