You just have to read the list of mods in order, when a ModState is missing, the mod cause the problem
for example:
AdvancedReactors{1.0.5-exp} [Advanced Reactors] (AdvancedReactors-1.6.2_1.0.5-exp.jar) Unloaded->Constructed
AdvancedThaumaturgy{0.0.7} [Advanced Thaumaturgy] (AdvancedThaumaturgy-0.0.7.jar) Unloaded
arsmagica2{1.0.2b} [Ars Magica 2] (AM2_1.0.2b.zip) Unloaded
AdvancedThaumaturgy is the first mod where the stats Constructed is missing, so this mod is causing the problem. Remove it