Go to the folder that contains your catalogs and look at the dates. The one with the most recent date would be the one that you have been using. However, if it has become corrupt it will be difficult to recover it. It might be better to replace it with your most recent backup. You can double-click on the catalog file itself and Lightroom will start and try to open that catalog. But if it is corrupt there isn't a lot that you can do.
- Please create a copy of Lightroom Default catalog.
- With Lightroom closed Navigate to Pictures/Lightroom and copy Lightroomcatalog.lrcat to your desktop.
- Also check what is the size of that catalog.
- Now open Lightroom and select Lightroomcatalog from the Prompt.
Let us know if that opens the correct catalog with all your images.
Thank you. I took a chance and selected the most recent dated catalog as you suggested - the one named simply Lightroom Catalog.lrcat. For whatever reason, LR opened right up and things appeared fine. I took an immediate backup, deleted the other catalog, and changed preferences from 'load most recent catalog' to specifically choosing the .lrcat file. Quit and restarted LR and still fine. No idea what caused the original hiccup - which makes me nervous. Only thing I can think of is the last thing I was doing before I got that error was importing some very old pics (pre-LR) taken on an iphone that had been edited in a variety of folders in addition to the folder I chose for import. Maybe LR just got confused.
Thank you, Akash. I tried the advice from JimHess and that seemed to do the trick. If I have further problems I'll try what you suggest.