Fix glitch please

I LOVE THIS GAME, but theres a bad glitch with it. My friend just got this game so he had nothing good, and when he joined me the glitch happend where he got all the weapons I had. Now when he plays with me the screen goes dark and he has the exact setup i have and money, even the upgrades copy, PLEASE FIX!!!!!!!!!

KatyJoy about Zombieville USA 2, v1.6.1