Lightroom won't restart

Hello:

The following sequence occurred with my Lightroom software:

1. Lightroom froze
2. After waiting for awhile, I turned off the computer
3. I turned the computer back on
4. When I clicked on the Lightroom icon, I got the following message: "The Lightroom catalog named "Lightroom catalog" cannot be opened because another application already has it opened.
5. I am then given three options:
   1. Choose a different catalog
   2. Continue
   3. Exit
6. None of these options results in the software opening.

I suspect that the software did not close properly when I turned off the computer. But I am not sure what to do.

Thanks,

Mel