Try turning off the Graphics acceleration
Go to Preferences, click on the Performance Tab, then UNcheck the box.
Sorry for the crashing, as dj_paige rightly recommends, it could be graphics card or driver related. Which version of Yosemite are you using?
Try turning off the GPU acceleration and see if that helps -- Adobe Photoshop Lightroom Help | Lightroom Graphics Processor Acceleration (GPU) Troubleshooting & FAQ
Another thing you could try is updating Lightroom to Lightroom 6.1.1 (don't update to 6.2.1 at this time) -- Download link is available here: Download Photoshop Lightroom
Let us know how it goes for you.
Thank you. Disabling accelerator worked. Unfortunately I had decided to
update 6.2.1 before getting your note but still not having crashing problem.
Thanks very much
Thanks very much. That worked. As a mac user, knowing what a graphics
acclerator is and then finding it is a challenge BUT your instructions fixed