I vaguely recall a BA 744 which diverted with reports of smoke in the flight deck which I believe did turn out to be the locking system on the flight deck door. I believe it was a couple of years back, and I think the aircraft was en-route from the Far East into Heathrow... I think I remember them saying they were more than slightly concerned!
Either way, whatever the cause of the smoke in the MD11 it's good to hear they landed safely... Job jobbed
my recollections are very vague - please correct me if I'm wrong!