iMovie hung reading iMovie Library.imovielibrary

This is probably the first time I've tried to open iMovie at least since upgrading to Yosemite - maybe longer. iMovie has been hung for hours now saying "Reading "iMovie Library.imovielibrary" library. I can't do anything with iMovie. I can't even quit it though I suppose I could do a force quit but I haven't tried that yet, hoping that at some point it would finally finish whatever it is doing. After 5-6 hours, I have given up on that hope. Does anyone have any suggestions?

Thanks.