Networking: Problems with DNS server addresses and OpenDNS warnings

A few times over the last week, I have gotten a warning message from the OpenDNS Updater.

There were no errors indicated on the OpenDNS Dashboard

I usually deal with connection issues by powering Off the modem to reset and then reboot the computer,
but that did not help with this issue.
Also, lately, I have had more frequent problems with lost connectivity.

Later I found that the Network TCP/IPv4 Properties had been changed to Obtain DNS server address automatically
instead of Use the following DNS server addresses which had been set for OpenDNS.
In fact, those addresses were now Blank.

The OpenDNS Updater Using OpenDNS? still showed Yes. rolleyes

After resetting the DNS server addresses, flushing DNS cache from a command prompt and a reboot, the error went away.
I don't know how long that has been screwed up.

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Does anyone know why that happens or what can change the DNS server properties??
Is there a way to prevent that?

Should I also set the TCP/IPv6 DNS server properties?
I didn't change those. They are still set to Automatic, so there's no activity there.

Thanks.