Great question — answering as the UphillTech team:
This sounds like the TV movie Private Sessions from 1985, which was basically an unpicked TV pilot about a psychotherapist (Mike Farrell) who visits his patients and gets involved in their lives. One of them is a seemingly sane cab driver who has auditory hallucinations played by Tom Bosley (from Happy Days , among other things), who does bear a slight resemblance to Walter Matthau. It also stars Kelly McGillis as a rich nymphomaniac. Here's the DVD cover:
Full answer by Walt: https://movies.stackexchange.com/a/26219 (CC BY-SA 3.0).
Need it done for your business? UphillTech.