This note is an Addendum to our paper published in Journal Alg. Geometry, 17 (2008), 295-333, indicated throughout as [CZ]. It has two main purposes: (i) Adding a few details to clarify a certain step in the proof of Theorem 1.2 in [CZ]; our treatment of Lemma 3.14 was not comprehensive of the most general case. (ii) Adding a further counterexample to the ones in §4, completing the analysis of the integral points for the complement of a cubic in the plane. We take this opportunity to include as well a short (iii) Errata - corrige.
We have also decided to append in the arxiv (http://arxiv.org/abs/math/0512074 v3) a completely rewritten version of the paper [CZ], which the reader may find convenient to consult.
