Hi, I have an electrical problem with my 2008 ( 5th gen ) 3.8 petrol GV ( 60,000 miles ). It has happened a couple of times now. Whilst driving, there is a "bong" from the OBC, loads of lights flash on the dashboard, speedo cycles down and up, then everything goes back to normal. The engine doesn't falter, but it's starting to cause concern. Any ideas ?