"Further investigation quickly established what it was that had happened. A meteorite had knocked a large hole in the ship. The ship had not previously detected this because the meteorite had neatly knocked out that part of the ship's processing equipment which was supposed to detect if the ship had been hit by a meteorite."

The book ("Mostly harmless") and especially the beginning of the first chapter is worth reading as it describes how the automated systems of the space ship try to resolve the situation.