HELP!! MuseScore Does Not Open Successfully

Hi: I have an Apple Macbook Pro. I'm running OSX Yosemite. -- I've had MuseScore for about 4 years and I use it every day. I used the software yesterday. Today, when I clicked on the icon to open MuseScore, it failed. The MuseScore 1.2 box displayed, as usual, but then another MuseScore error box superimposed itself. [ "The last time you opened MuseScore, it unexpectedly quit while reopening windows. Do you want to try to reopen its windows again? ] -- After that, there's a sub-message, as follows: "If you choose not to reopen windows, you may have to open and position the windows yourself." Then there are two bars, one is marked "Don't Reopen" and the other is marked "Reopen" and is blue, as if that bar is some sort of default. -- IF I click on the "Reopen" bar, the message screen disappears but then I get a full-screen error (I think from Apple) entitled PROBLEM REPORT FOR MUSESCORE. That screen says, "MuseScore Quit Unexpectedly" It gives me the option to reopen and tells me that the error screen contents will be sent to Apple. -- Of course, this doesn't solve MY problem. Can anyone help me change things so that MuseScore will work again?