This mutator was never all that stable for me since the update last Christmas. I decompiled it, made some changes, and recompiled it. Now it works on IceCave. For the time being I have removed ESL since for some reason which I have not taken the time to figure out yet, it keeps on causing my game to crash when this mutator is selected and I am on that map. All I have done aside from changing the map is I have added "#exec OBJ LOAD FILE" lines in the KFGameTypeXMAS.uc file for the different utx and usx files to make sure it has no problem in finding them.
When I have a chance, hopefully on Tuesday, I will review the files thoroughly and see if anything needs to be removed, added in, or modified.