If it's just that one spot, relief doesn't sound like the answer to me. It's possibly a slight inconsistency in the plane of the fingerboard just bridge-side of the note G (and Ab). You might try a bit of 0000 steel wool to see if you can even out the board, but you can get yourself into trouble pretty quickly if you over-do it or if the problem is something else.
I'm not sure what type of bridge it has, but if you can raise the action just on the D to see if the buzz goes away, that might pinpoint that it is a discrete high point on the board. If you have to raise the whole bridge, so it be it - it's just a trouble-shoot. If you don't feel comfortable doing it yourself, if it is just a small area that needs taking down, it should be a fairly easy and inexpensive job for a good luthier. Depends on whether the board is finished too.
Tuning a mellotron doesn't. - Robert Fripp
Last edited by FretlessMainly : 12-17-2012 at 09:17 PM.