OK, my searching seems have borne fruit. Although a bit old, this article directly addresses the issue I described above (although relating to a different domain.)
http://installingcats.com/2008/06/01...ckups-backupd/
The issue is a result of an OpenDNS action for unknown domains (as described in the article) and, it turns out, I had just enabled OpenDNS recently. Specifically, it seems that by using an OpenDNS advanced feature called Domain Typos, you can specify for OpenDNS to not send back the offending info that causes the symptom.
So, as Shirt Pocket said,
NOT a SuperDuper! problem at all, but it just happened to expose a symptom of how automountd interacts with OpenDNS (and some other DNS systems.)
Thanks, all, for your assistance.