There are people who play Quake, and then there are people who live and breathe it. An example of a shader problem.
Software patches a game.
Now let's jump in and see if we can't help some players. For a full list, always read the Readme.txt that places itself in the Quake III base directory. It clearly states in the new readme that this is a known issue. Here's the blurb ripped right from the text. Known Issues - Launching demos from the user interface does not work.