  Regularity theory in generalized function algebras of Colombeau type is
largely based on the notion of ${\mathcal G}^\infty$-regularity, which reduces
to $C^\infty$-regularity when restricted to Schwartz distributions.
Surprisingly, in the nonstandard version of the Colombeau algebras, this basic
property of ${\mathcal G}^\infty$-regularity does not hold.
