The Dink Network

I am towards the end of the game with the Zombie garding the exit. I have skard and Cthunik (he can cast the sleep spell) at first everything starts well. I have Cthunik cast the sleep spell and I throw the death star until he gets close. after a few times the sleep spell stops working for a minute and thats fine because I know its weak but when I drink more life from my potion to "re-up" after being hit to much by the zombie while waiting for Cthunik to get his sleep spell back, The screen freezes. Any suggestions or help out there?

Kill the zombie without the sleep spell, and try killing him with the death SWORD, not with the death STAR. If you try to kill it with a throwing star and if your computer is not 'powerful' enough, the screen may freeze.
Kill it as soon as possible. Do not lose time with Skard or Chtunik's sleep spell.