Update: If I, as APREA Thomas says, enable Power Manager as a Startup Program under System->Preferences->Sessions the hang does not happen. And all four buttons (Restart, Shutdown, Suspend and Hibernate) appear at the bottom of the "shut down dialog".
Update: If I, as APREA Thomas says, enable Power Manager as a Startup Program under System- >Preferences- >Sessions the hang does not happen. And all four buttons (Restart, Shutdown, Suspend and Hibernate) appear at the bottom of the "shut down dialog".