Did the Protestant work ethic cause the rise of modern capitalism?
Not exactly, but the following video is a good breakdown of the subject. Basically, the Medieval Catholic liturgical calendar was packed full of holidays and other rest days from work. Western Europeans worked significantly fewer hours than they do today. By glorifying labor, condemning idleness and eliminating the Catholic calendar, Protestants in Northern Europe worked more and accumulated more capital, especially the English and Dutch who became involved in long distance trade with Asia.
Note: In case you are wondering, I have been intensely researching the late Reformation/early Enlightenment period of European history as part of an ongoing project of examining the ideological headwaters and spread of liberalism.