Some yeasts produce a very sulfurous smell when they are fermenting. If this is a bottle conditioned beer, it could be that that bottle had a higher concentration of yeast (was there yeast residue in the bottom of the bottle at all). Maybe that yeast was either still fermenting out, or had produced more of that sulfurous gas than the other bottles. Just a thought. Of course if we are talking about some big time beer lim Sam Adams, then something else is going on.