a buzzing classical d string

[Lucille Nailor]

well I have just taken posession of a beautiful Madrid made classical guitar with a wonderful full sound . It came from Spain to Melbourne then to me in Queensland Australia. BUT on the 6th fret, 5th and 4th when these notes are played reststroke they buzz. But not freestroke. the action is low as it is very playable and it is a 640 scale.Wondering should I raise the saddle a bit witha strip of wood?

[Mike Kolb]

So many variables to a buzzing condition.... it's almost impossible to diagnose without the instrument in-hand.  That said, here's a great place to start the investigation: 

http://frets.com/FretsPages/Luthier/Technique/Setup/BuzzDiagnosis/b...