Null pointr exception

[INFO] Starting minecraft server version 1.4.7
[INFO] Loading properties
[INFO] Default game type: SURVIVAL
[INFO] Generating keypair
[INFO] Starting Minecraft server on *:25565
[INFO] Preparing level "world"
[INFO] Preparing start region for level 0
[INFO] Preparing spawn area: 63%
[INFO] Done (1.567s)! For help, type "help" or "?"
[SEVERE] Encountered an unexpected exception t
t: Ticking tile entity
    at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:686)
    at ho.r(DedicatedServer.java:269)
    at net.minecraft.server.MinecraftServer.q(MinecraftServer.java:599)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:497)
    at fy.run(SourceFile:849)
Caused by: java.lang.NullPointerException
    at gregtechmod.api.BaseMetaTileEntityMJ.powerRequest(BaseMetaTileEntityMJ.java:51)
    at buildcraft.transport.PipeTransportPower.updateEntity(PipeTransportPower.java:164)
    at buildcraft.transport.Pipe.updateEntity(Pipe.java:166)
    at buildcraft.transport.pipes.PipePowerWood.updateEntity(PipePowerWood.java:80)
    at buildcraft.transport.TileGenericPipe.g(TileGenericPipe.java:189)
    at yc.h(World.java:2153)
    at in.h(WorldServer.java:516)
    at net.minecraft.server.MinecraftServer.r(MinecraftServer.java:680)
    ... 4 more
[SEVERE] This crash report has been saved to: D:\Download\MindCrack_Server(1)\.\crash-reports\crash-2013-05-30_11.51.50-server.txt