Not sure if it is in earlier version or not.

cpw.mods.fml.common.LoaderException: java.lang.NoClassDefFoundError: com/carpentersblocks/renderer/helper/FancyFluidsHelper
at cpw.mods.fml.common.LoadController.transition(LoadController.java:162)
at cpw.mods.fml.common.Loader.preinitializeMods(Loader.java:515)
at cpw.mods.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:88)
at cpw.mods.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:314)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:117)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:387)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)
Caused by: java.lang.NoClassDefFoundError: com/carpentersblocks/renderer/helper/FancyFluidsHelper
at com.carpentersblocks.block.BlockCoverable.func_149662_c(BlockCoverable.java:1403)

That is the important part of the log.
Turning off the dynamic fluids on slopes will allow it to start.

public boolean isOpaqueCube() should probably be client side only, or at least check if it is client or server before trying to load the renderer helper class

Thanks for the report. I will look into it.

You were right 👍