This is reassuring (not): "An A340 operator reported the loss of ISIS followed, during the same flight, by the loss of all Electronic Instrument System (EIS) Display Units (DU). The failure mode of ISIS has been identified as a time counter fault after 145 hours of ISIS continuous power supply. AD/A330/28 (DGAC AD F-2004-117) mandates the operational procedure to recover lost EIS Display Units, pending a new EIS standard addressing the misbehavior. Situations where EIS DUs and ISIS are simultaneously unavailable may result in hazardous consequences in certain phases of flight. This Directive requires a periodic on ground-reset procedure to prevent the ISIS failure by clearing the time counter." AD/A330/42 Integrated Standby Instrument System 13/2004 The temp fix was to cut power to the ISIS for more than 5 secs so it would reset.