I think you can blame the zucchini for the strange flower troubles. Some of my zucchinis grow rather large without the flower ever opening. If they aren't picked they they die similar to the way you described. I only ever notice this strange behavior early in the season, as the plant matures I don't notice the problem anymore. I have never seen this problem on acorn squash. I wish I could tell you what causes this I am rather curious myself. It doesn't sound like a serious problem though as long as some are opening you will get fruit. In the future you should just pick the ones that grow but fail to open and eat them as summer squash.

It seems like now that the plant is larger it's flowering much sooner. But I was hoping to see that one flower. Oh well. I have plenty more. Now lets hope they taste good.