We can get to the bottom of this if you run the following experiment:

Install steam CMD: http://media.steampowered.com/client/steamcmd_win32.zip

In the folder you install that in create a .bat file with the contents:
Code:
SteamCmd.exe +login username pass +force_install_dir C:\game_servers\ns2 +app_update 4940 verify +quit
  pause
WHERE username and pass ARE YOUR STEAM USERNAME AND PASSWORD

Then run the bat file to install the dedicated server:

Then go to: C:\game_servers\ns2

Create a .bat file with the following contents called snow.bat
Code:
Server.exe -name "Test" -port 27017 -mods "a02b93d" -map ns2_biodome -limit 19 -webadmin -config_path C:\game_servers\ns2\cfg -modstorage C:\game_servers\ns2\mods
Run this file after you create it and your dedicated server will start.

Open ns2 and then join the server called Test or in console type connect localhost:27017

If you crash the problem is snowballs. Also try to toss a snowball.