"Unexpected error opening catalog"

My Lightroom was working just fine. I was actually in the middle of importing photos when all of a sudden it froze and crashed with an error message that said something about the catalog. I don't remember exactly what it said that time and if it was the same error message. It closed and now when I try to open it, it does not open but instead says "Unexpected error opening catalog". The options are Try Again (doesn't work), Quit (not what I want) or Choose a Different Catalog. When I try choose a different catalog, it gives a couple of options but that doesn't work either.