Turn off antivirus or other "network" programms, cuz gameguard can detect it as illegal software and crashing...
happened here too damn often, allways while running world of warcraft, guess the b.net agent crashed it
Make sure that you are only running the 12sky game client since this might conflict with other programs as mentioned by players above. Also check the Anti-virus software or firewall to see if its prevent the launcher, GameGuard, or game client from launching.