SOLVED: The problem turned out to be that the group was not nil, but the pointer pointed to a group that had already been removed. As a result, it was not a valid parent group and I was unaware of this until after further debugging. For example:
group = display.newGroup()
copyOfGroup = group
display.remove(copyOfGroup) --this will actually eliminate the original definition because the group object itself is not copied, but the pointer instead.
And therefore, group:insert(object) will fail as will any attempt to include it as a parent group for new objects.
The Corona syntax for display.newCircle is located at: https://docs.coronalabs.com/api/library/display/newCircle.html
The syntax is:
display.newCircle( [parent,] xCenter, yCenter, radius )
In the daily build 3350, the parent group is not always accepted and I receive the message that a number is expected and not a table.
For the longest time I have been using "group:insert(object)" to manage my groups, but in my newest App that it is Beta, I am always assigning the parent group when defining an object. Has anyone experienced this problem?