>Could it be that one of the views was closed?

That was it.

The problem was not with views opened by another object, but with views that are opened by this object.
These views are opened in the Init event for Object 2.
However, the Init events for the controls in the form object are executed before the object's own Init event. The error was occurring in one of these.

I moved the view creation logic to the Load event and the error went away.

Looks like there's a difference here between initialization of a form and initialization of a form object.

Many thanks!
Howard