SWJN5

When launching Voltz the launcher sayes there is a duplicate mekanism file. Error is "Forge Mod Launcher has found a problem with your minecraft installation you have mod sources which are duplicate in your system mod id : file name meckanism : mekanism.jar mechanism : mekanism-v5.2.0.jar" The launcher just sits there doing nothing. Minecraft and other mods work alright. Any ideas????????