I came across this article by a Roman Catholic priest.
Apparently all Christians, even in the West, made the sign of the cross the (now) Orthodox way. As you can usually guess with Catholic-Orthodox history, this changed when Pope Innocent III decided to change things and have Western Christians go left to right shoulder. It makes more sense now that he ordered the crusade which sacked Constantinople in 1204 as well.
I was curious why my Lutheran pastor crossed himself 'the Orthodox way', and now I see why. I too will join the Orthodox in making the signum crucis right to left.