Freeze on destructible terrain.

Hi, I've been working on a worms clone. I have a script which uses a binary image for the terrain, and I edit it to show explosions, etc. Here is the code: http://pastebin.com/RKCgPikJ

I've tried adding co routines and the such, but everytime the damage function is called, I get a momentary freeze.

Given that worms had this functionality on far more primitive machines, I know there must be a way to get rid of the freeze.

Any suggestions? Thanks in advance!