I have been having sporadic, but rather frequent, problems with various operations on the admin pages causing first a freeze of the page and then, when I either try to reload or click on any of the controls, I get kicked back to the login screen and have to enter the admin ID and password again. After doing that, I am taken right back to the page I was on, so it's not really a complete logout, but rather a reauthentication.

I am now on build 160812, but this problem has been present ever since I started using LimeSurvey on build 160705.

Any ideas how to fix this?

Try increasing the session time in Global settings - www.limesurvey.org/manual/Global_settings#General