Netduino + Mosfet Driver + PMDC Motor = Magic Smoke
4700&Omega; on the gates of the MOSFETs is far too high. These should be no more than about 100&Omega;.

With such a high resistance, the MOSFETs are switching far too slowly and dissipating way too much power, especially when the motor isn't actually running yet and passing its "stall" current.

Also, what is C2 in there for? Probably should be deleted.

One more thing: Although the body diodes on the MOSFETs will protect them somewhat, it would probably be better to add a beefy freewheel diode directly across the motor.