LEAP 15.1 System freezes at log-in screen

I installed Leap 15.1 with no problem. It booted OK, but after I installed Zoom and Thunderbird, I could no longer boot the system. It freezes as soon as I type in my password and press enter.

After encountering this problem for the first time, I reinstalled and tried again. The second time I installed Zoom, rebooted successfully, and then installed Thunderbird. At the next reboot the system froze.

I don't know if this problem is a a result of the TBird installation, if it is the combination of Zoom and Tbird, or it is something else entirely. Any help will be appreciated. I would really like to give openSuse a try.

Richard