Saving chunks -> white screen

[Ganondwarfy]

Title: Saving chunks -> white screen

Version: 3.1.3

OS: windows 8

Java Version: v7 update 10

Description of Problem:

I just started doing railcraft stuff in tekkit and as sooon as a cart hits the booster rail it goes to a saving chunks screen then white screen. help?

I have re-downloaded the technic launcher, my drivers are up-to-date, i am using 64 java, and have chosen to allocate 4gb RAM to tekkit out of my 8gb.

help???? i have been trying to figure this out for a day now. and have tried many things that don't work. i am using BDcraft texture pack and no mods other than tekkit.

Also i am not on any multiplayer server, im doing SSP. please dont ban me, i didn't know which section to put this into.

Error Messages:

none

Error Log:

java.lang.ArrayIndexOutOfBoundsException: 4

at railcraft.common.utility.TileUtilityItem.a(TileUtilityItem.java:61)

at railcraft.common.utility.TileMultiBlock.a(TileMultiBlock.java:250)

at railcraft.common.utility.TileMultiBlock.a(TileMultiBlock.java:254)

at railcraft.common.api.InventoryMapper.a(InventoryMapper.java:46)

at railcraft.common.api.InventoryTools.moveOneItem(InventoryTools.java:375)

at railcraft.common.utility.TileItemLoader.moveItemToCart(TileItemLoader.java:252)

at railcraft.common.utility.TileItemLoader.n_(TileItemLoader.java:203)

at xd.n(World.java:2081)

at net.minecraft.client.Minecraft.k(Minecraft.java:1871)

at net.minecraft.client.Minecraft.x(Minecraft.java:825)

at net.minecraft.client.Minecraft.run(Minecraft.java:753)

at java.lang.Thread.run(Unknown Source)