when i open up the steam crafter thingy, it crashes with the error (it has been shortened for readabity):
Client thread/ERROR]: Exception caught during firing event net.minecraftforge.client.event.GuiScreenEvent$InitGuiEvent$Post@1a26af22:
java.lang.AbstractMethodError
at vazkii.quark.base.handler.DropoffHandler.isValidChest(DropoffHandler.java:120) ~[DropoffHandler.class:?]
at vazkii.quark.management.feature.ChestButtons.initGui(ChestButtons.java:57) ~[ChestButtons.class:?]
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_457_ChestButtons_initGui_Post.invoke(.dynamic) ~[?:?]

Don't truncate your log, this removes important information. Post all of it on gist or pastebin. Make sure you have the latest version of quark.