The official Quake III Arena FAQ has undergone a minor update (thanks Ryan Stotts). Here's the whole update, which addresses a common CTF problem:

Why does the game sometimes crash if we callvote to another level while playing CTF?

In version 1.11 of Quake3 the game will crash if players try to run a CTF game on maps not designed for CTF. Do not perform a callvote requesting a map change to a non-CTF map without changing the game type first. Before changing maps always make sure you have the correct gametype set.

g_gametype 0 – Free For All
g_gametype 1 - Tournament
g_gametype 2 – Single Player
g_gametype 3 – Team Deathmatch
g_gametype 4 – Capture the Flag

This crash will be fixed in the first point release of the game.