In fact, if the diagnosis differs from what the computer says, then this should always be reported. Failure to do so should be considered a criminal offense.
Penalties are certainly a mistake in the case of your statement, as you haven't really outlined any computerized diagnostic system that is accurate on the entire range of human maladies, is available to all, and that can account for all of the fuzziness of reporting symptoms (just to name a few obstacles).
But I can't see at all where you're coming from when you say criminal offense. This would suggest that doctors should be locked up?
Then you feed it all the symptoms, sometimes it asks questions, and gives you a list of causes sorted by probability.
It works almost exactly like this game http://www.guessthename.com/
Apparently the biggest problem with it is that doctors won't use it.
The second problem is feeding data - you basically have to parse every medical paper ever published.
Here's a patent: http://www.freepatentsonline.com/6607482.html
There are lots of a papers, and a small number of working prototypes, but I have not heard of any that are actually being used.