HABEN and SEIN?

The students know when to conjugate verbs with "haben" and when with "sein" in the present and past perfect tenses, active voice, indicative mood. They are confused, however, when they see or hear what they perceive to be "haben-verbs" used with "sein" and "sein-verbs" used with "haben." Why are they confused? What confuses them? The teacher tries to explain some of the reasons in this podcast.