Relevant part of the MT log: http://pastebin.com/65ELNuA1

Looks like the input and output objects are reversed or something? At any rate, checking the affected recipe will either show that it isn't properly removed (if you haven't reloaded scripts in the current session) or just crash the game (if you have). Crash log: http://pastebin.com/eDGCX3Kk

Fixed in ModTweaker2 0.9.0. Please update! (Also update Mekanism to v8)

I got trouble too with the metallurgic infuser since 0.7.2,
between 0.7.2 and 0.7.4 the script just dont work but with the 0.7.5 it crash the client

I commented on this in issue #102 The problem is that the Mekanism API has changed and ModTweaker is referencing classes that no longer exist. Specifically
import mekanism.api.infuse.InfusionInput;
import mekanism.api.infuse.InfusionOutput;