Navigation and Multipurpose Display

Navigation/FMS: (Flight Mirabel Canada to Incheon South Keroa-747) The navigation and multipurpose display (routing display) bug down during flight as the route displayed was at least 80 nm to the left of actual aircraft. Attempts to regain the route was futile as it appear frozen. However countdown to next waypoint was functional. This happen in the polar route regions and the route information came back once coasting in Russia. Obviously a bug.