There were in fact two major frondes:

The first consisted of members of the Parlement. Paris had a system of investments known as rentes---basically, government-issued bonds. In the mid-seventeenth century, Mazarin, minister and de-facto ruler of France, systematically bought large numbers of rentes low, paid off some of the interest, and sold them when the price rose again. This caused massive depreciation; those who had investements in rentes were not amused. As historian David Ogg put it, ``It is possible to crush a peasantry so that it cannot rise, but systematic robbery of a prosperous and educated bourgeoisie generally ends in revolution'' [Europe in the Seventeenth Century]. The fronde, however, lacked the unity of principle and purpose which had allowed the Civil War in England to produce dramatic results.

The second fronde consisted of members of the nobility, and lasted longer than the first. Many historians attribute it to the pent-up anarchic tendencies of the nobility. I know less about this one, so I'll leave it for others to write up.

For more information, I recommend:

David Ogg. Europe in the Seventeenth Century. New York: Collier Books, 1960.