I'll offer another explanation: In our section of the country, we are having severe problems with melons and squash due to lack of pollinators.  Yep, our little world-wide bee problem is becoming really noticable now.  The fruit starts, but then shrivels up because it hasn't been properly pollinated.  You can try hand pollination to see if that solves your problem, or you can spray with bee pheromones to help attract more bees.