Lorinda – Thanks for the reply. That would have been the best place to start, and I'll do that next time.
I went ahead and pulled the Accordance Files out of my Documents folder and onto the Desktop. Did the same for the Accordance folder in Application Support. Then I reinstalled (took only a couple of minutes), dropped my modules and a bunch of the other things back where they belonged . . . When Dropbox synced, I got uncorrupted prefs and User stuff back and all is well.
Just trashing the Start-Up would have been quicker!
In all this I found myself very grateful for Dropbox, and the knowledge that TimeMachine was up and running. I knew I'd be able to get my stuff back one way or the other. Thanks go to the Accordance Team for well designed software, and to Apple for well-designed machines, OS, & back-up system. And thanks to this forum for all the helpful and knowledgeable folks!
MacBook Air Yosemite
mid-2013 1.7 GHz Intel Core i7 (2 cores)
8 GB RAM; 512 G SSD
Mac mini Yosemite Acc 11
late-2012 2.3GHz Intel Core i7 (4 cores)
16 GB RAM; 1.12 TB Fusion Drive
iPad Air 1 iOS 8.1