Hi Betsy,

You could get the top nut checked out - it might be that the strings are pinching in the slots, so moving as soon as you play, or the nut slots could be too high, making the thing play sharp (a condition present on most instruments "out of the box"). Hard to tell without seeing the instrument, but I'm in the South-East of England. I'm not a "Martin Approved Luthier", but repair and set up instruments, including Martins, Taylors, Gibsons etc. for a living.

Martins do seem to be sensitive to temperature and humidity changes. I played outdoors for a house concert one damp evening, and my D12-28 simply would not settle. HDs are built light, but my money's on something simple being wrong.

Hope you get it sorted - if you do you should have an absolute beauty to play.

All the best,

Brian