According to wikipedia, that had software problems that ended up killing people What's that got to do with UI changes and user experience?
The original post was about bad user interfaces causing harm to people. Changes breaking the user experience was only one of the issues.
In Therac's case the bug WAS primarily in the user interface:
- Due to a race condition, if a button happened to be pressed at the wrong moment and the menu filled out in a particular order, the device would configure the electron beam for x-ray generation rather than electron beam generation (high electron beam current, no scanning) but not position the target, flattening filter, collimator, or ion-chamber x-ray sensor in the beamway, resulting in a configuration that irradiated the patient with beta radiation, rather than x-rays, at 100x a normal dose.)
- The machine DID detect that there was a problem. But it reported it as "MALFUNCTION nn" - where nn was a number from 1 to 64 and not explained in the manual. If the operator entered "P" (proceed), it would then go ahead and operate in the improper mode anyhow.
Both the second part and most of the first part sound like user interface problem to me.