I have discovered a glitch that causes the game to lock up and screen to flash. This is due to the particle system that creates Riser zombies. I will find a solution and update it soon. Thanks for all your help.
I'm still investigating the weapons switching glitch some have reported, it seems like it might be a Chrome issue too, as I haven't seen it on Firefox.
ZebraHumor
The only zombo in my life is http://zombo.com/