sarah,
sounds like you may have had the same problem i did. though i cant really tell by not actually knowing a lil more detail of your watering habits, fertilizing, and much much more, you may have encountered the dreaded squash bug!
This dude managed to completely devestate my zuchini
plant in a matter of days. My
plant started off by looking like it was wilting. At the time it was considerably warm where we live, around 95 deg for a good 4-5 days straight. I watered a lil more extra than normal, but it was still wilting bad. Finally had to cut it completely out, and upon doing so i saw that ugly monstrosity of a bug in my
plant. I promptly checked out my squash
plant and saw the same bugs, and even on my cucumbers! I had no choice but to spray some Seven on them. . . it was a dreaded time of desperation lol