Have you noticed any honeybees? Many of us are noticing the lack of them, since nearly half of all the US honeybees died over this past winter.
They are pollinators for squash.
When the female flower appears, there is already an embryo squash behind it. If the flower does not get pollinated (enough - it takes more than one visit), the squash will still grow for awhile, usually getting to be a couple inches long or so (sometimes more) and then it will shrivel up and drop off.
https://gardening.pineapplepalace.org/wp ... C05555.jpg
squash from unpollinated flowers
Alternatively, squash (and other cucurbits) , like tomatoes, can get blossom end rot. The blossom end of the squash gets very dark, brown or black, and soft/ rotten.
https://www.uaex.edu/yard-garden/resourc ... %20rot.JPG
Blossom end rot (in tomatoes and squash) is due to calcium deficiency, but it is almost never a lack of calcium in the soil. Rather various kinds of stress make it difficult for the plant to uptake/ transport calcium. Uneven watering with lots of wet / dry cycles can result in BER. Also if your soil pH is too high or too low, it can interfere with calcium uptake. Too much high nitrogen fertilizer can cause an imbalance of growth between the roots and the leaves. If the leaves grow too fast, the plant does not have enough roots to take up calcium the squash fruit will need. If you fix the problem, then fruits that are set afterwards will not get it.
Do either of these seem like what is going on?