Почему не работает minecraft ID resolver ?

резольвер требует GuiAPI (ну и фордж конечно)
оба джара надо положить в coremods
оф. страница
если все верно - смотрите логи

"Block hook is disabled or not working! Block conflicts will not be resolved correctly."
OR
"Item hook is disabled or not working! Item conflicts will not be resolved correctly."

This means that ID resolver wasn't able to detect that it's resolving method for Blocks or Items was called. Basically, you didn't install the mod right. It has to be installed as a coremod, which is to say you copy the jar downloaded to .minecraft\coremods. That's it. After that, when Minecraft launches, FML will see it and make the patches needed.