Here's the report from Avherald:
Incident: Singapore A388 over Andaman Islands on Apr 26th 2012, navigation system problems
A Singapore Airlines Airbus A380-800, registration 9V-SKQ performing flight SQ-318 from Singapore (Singapore) to London Heathrow,EN (UK), was enroute near the Andaman Islands about three hours into the flight when the crew decided to return to Singapore due to problems with the navigation systems and autopilot. The crew dumped fuel on their way back to Singapore. The aircraft landed safely back in Singapore about 6 hours after departure.
The flight is now estimated to depart Singapore with a delay of 11 hours.
Passengers reported the crew wasn't very clear in their announcements, they understood technical problems with the navigation systems that also knocked the autopilot off.