On the menu bar, between the Edit and Navigate menus, is a "%Refactoring.menu.label" menu. It contains three menu items: "%Refactoring.undoAction.label", "%Refactoring.redoAction.label" and "%Refactoring.renameAction.label". Clicking on any of these menu items pops up a dialog saying that "The chosen operation is not enabled" and then the menu item is disabled.
After switching to the Java perspective, the %Refactoring.menu.label menu is filled with lots of other (valid) menu items, but the strange ones stay put. %Refactoring.undoAction.label and %Refactoring.redoAction.label are still at the top of the menu, followed by Undo and Redo, then %Refactoring.renameAction.label and then Rename, Move, Change Method Signature, etc.
*** This bug has been marked as a duplicate of 158951 ***