We can first try resetting your configuration in LightRoom to it's defaults, as it appears that the preferences file is corrupt.
First, you will want to record any preferences that you wish to keep in Lightroom.
- In LightRoom, in the top menu bar, click Lightroom > Preferences
- Make a note of all the settings and close that window.
- In LightRoom, in the top menu bar, click Lightroom > Catalog Settings
- Check the "General" tab and make note of it's location.
Resetting the Preferences file:
- Close Lightroom before you continue.
- Go to the [username]\LibraryPreferences folder. Replace [username] with your username.
- Drag the com.adobe.Lightroom....plist file to the Trash folder.
- Now you can re-open Lightroom and open your catalog by choosing File > Open Catalog. Navigate to the folder location that you made note of earlier and open your catalog.
Did that work for you?