Serverpack Direwolf20 (version 1.0.23)
OpenBlocks version: 1.2.7
Thaumcraft version: 4.1.0g

Step 1: Place a Vacuum hopper above a 'Arcane Pedestal' (thaumcraft)
Step 2: Insert item in Vacuum Hopper
Step 3: Set the item output of the Vacuum Hopper down (to the pedestal)
Step 4: Crash

I can't provide an error log since this happened on a public server.

Sorry for my bad english, I'm not a native speaker.

---- Minecraft Crash Report ----
// Quite honestly, I wouldn't worry myself about that.

Time: 07.07.14 16:56
Description: Ticking tile entity

java.lang.ArrayIndexOutOfBoundsException: -1
at thaumcraft.common.tiles.TilePedestal.func_70301_a(TilePedestal.java:49)
at thaumcraft.common.tiles.TilePedestal.func_102007_a(TilePedestal.java:297)
at openmods.utils.InventoryUtils.insertItemIntoInventory(InventoryUtils.java:114)
at openmods.utils.InventoryUtils.moveItemInto(InventoryUtils.java:182)
at openmods.utils.InventoryUtils.moveItemInto(InventoryUtils.java:125)
at openblocks.common.tileentity.TileEntityVacuumHopper.autoInventoryOutput(TileEntityVacuumHopper.java:157)
at openblocks.common.tileentity.TileEntityVacuumHopper.outputToNeighbors(TileEntityVacuumHopper.java:137)
at openblocks.common.tileentity.TileEntityVacuumHopper.func_70316_g(TileEntityVacuumHopper.java:132)
at net.minecraft.world.World.func_72939_s(World.java:2209)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:550)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:668)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:129)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)