Could be a high fret. Could be the relief. Could be the action -- either the nut slot or saddle height.
If it's buzzing after the setup, take it back to have the tech correct the problem.
If you want to be armed with some information, take a look at frets.com for some setup tips. E.g.:
http://www.frets.com/fretspages/luth...ef/relief.html