In late 2012, GameSpy ceased supporting many old games, including Gangland. As a result, only LAN play is possible*, and the game will crash when attempting to join a multiplayer game, unless changes are made to your firewall's settings.
To make LAN multiplayer work in GangLand, please block this IP in your firewall, for both TCP and UDP:
If possible, only apply this rule to GangLand. If you're using any other games that rely on GameSpy to search for available servers, and you set the IP block globally, you might need to disable/delete the block before playing those games.