Originally Posted by drwpk

That was interesting.

As per your suggestion, I downloaded and re-installed each of the 3/10 updates individually, and tested after each re-installation. I noticed that both security updates failed today in the middle of the installation the first time, and then were successful the 2nd time, again installing them separately from each other. Curiously, the tethering worked after each individual installation. Based on that, and on my observation of the installations' failing initially, I now suspect that the problem I had may have been related to an imperfect installation of one or both of the security updates from 3/10. The good news is that everything now is working fine, and with all updates to-date installed.