Thanks.
I found that it was the application_id in the aspnet_membership table. When a user is to become 'super', in addition to the flag in the Users table, the application_id in table aspnet_membership must match the application_id for portal 0 that is in aspnet_applications. In making this change, the symptons described in this thread went away.
For my purposes, the superuser permissions is only a temporary need so I won't have to clean out the userportals and userroles tables. In a windows auto-login environment, I need to only turn on the extra permissions while doing maintenance.
Jeff