Hi robertod19903257,
Sorry that Lightroom Classic CC is crashing while importing images and building previews. Which exact version of Lightroom Classic CC are you using(latest version is 7.4) and what is your operating system?
Please check the below steps to troubleshoot the issue:
1) Navigate to the preview cache location of your working catalog and delete the cache folder.It is located in the same folder as the Lightroom Catalog. The preview cache name ends with previews.LRDATA and should be deleted. **Do not confuse this with *.LRCAT, which should not be deleted.
The default location for the catalog preview on Mac and Windows(probably you are using it) are:
Mac:- /Users/[username]/Pictures/Lightroom/Lightroom Catalog Previews.lrdata
Windows:- C:\Users\[user name]\Pictures\Lightroom\Lightroom Catalog Previews.lrdata

2) As you've mentioned that your computer is crashing while importing images, which source are you importing the images from? Try importing some images from your local drive and see if the issue persists.
Regards,
Akash