I think I found where McAfee is interfering with the Dir-655 admin configuration screen and causing those obnoxious intermittent logouts.
It is, I believe, the McAfee "My Home Network" tool that is scanning the network for changes.
It begins to act up several hours after a computer reboot.
If I run Services.msc as administrator, stop the "McAfee Network Agent" service, the problem goes away immediately.
When I stop that service and visit the McAfee control panel, the "My Home Network" shows that it is disabled and it doesn't show any items on the network.
My only question now is if it is OK to run with the network agent service disabled. It would be very easy to set the service properties to 'Disabled' and never let it run again. The "My Home Network" tool is rather lame in any case, and it would be no great loss. It would also be easy enough to let it run and just stop/restart that service to clear up the problem when I needed to configure the router.