The following happens when using Mechanism in the All the Mods pack. The version seems to be 9.2.2.301.

I've built up a small machine park using Mekanism, but I can't use universal cables or the pressurized tubes: they disappear whenever I return from the Nether. The following appears to be a relevant section from the log file. Please let me know if you require any other information.

Description: Ticking block entity

java.lang.NullPointerException: Ticking block entity
at mcmultipart.network.MessageMultipartChange.toBytes(MessageMultipartChange.java:51)
at mcmultipart.network.MessageSplit.split(MessageSplit.java:94)
at mcmultipart.network.MessageMultipartChange.send(MessageMultipartChange.java:142)
at mcmultipart.multipart.Multipart.sendUpdatePacket(Multipart.java:340)
at mcmultipart.multipart.Multipart.sendUpdatePacket(Multipart.java:330)
at mekanism.common.multipart.PartSidedPipe.func_73660_a(PartSidedPipe.java:193)
at mekanism.common.multipart.PartTransmitter.func_73660_a(PartTransmitter.java:59)
at mekanism.common.multipart.PartPressurizedTube.func_73660_a(PartPressurizedTube.java:78)
at mcmultipart.block.TileMultipartContainer$Ticking.func_73660_a(TileMultipartContainer.java:328)
at net.minecraft.world.World.func_72939_s(World.java:1804)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:620)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:709)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:240)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471)
at java.lang.Thread.run(Thread.java:748)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Server thread
Stacktrace:
at mcmultipart.network.MessageMultipartChange.toBytes(MessageMultipartChange.java:51)
at mcmultipart.network.MessageSplit.split(MessageSplit.java:94)
at mcmultipart.network.MessageMultipartChange.send(MessageMultipartChange.java:142)
at mcmultipart.multipart.Multipart.sendUpdatePacket(Multipart.java:340)
at mcmultipart.multipart.Multipart.sendUpdatePacket(Multipart.java:330)
at mekanism.common.multipart.PartSidedPipe.func_73660_a(PartSidedPipe.java:193)
at mekanism.common.multipart.PartTransmitter.func_73660_a(PartTransmitter.java:59)
at mekanism.common.multipart.PartPressurizedTube.func_73660_a(PartPressurizedTube.java:78)
at mcmultipart.block.TileMultipartContainer$Ticking.func_73660_a(TileMultipartContainer.java:328)

-- Block entity being ticked --
Details:
Name: mcmultipart:multipart.ticking // mcmultipart.block.TileMultipartContainer.Ticking
Block type: ID #1695 (tile.null // mcmultipart.block.BlockMultipartContainer)
Block data value: 0 / 0x0 / 0b0000
Block location: World: (13,68,695), Chunk: (at 13,4,7 in 0,43; contains blocks 0,0,688 to 15,255,703), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Actual block type: ID #1695 (tile.null // mcmultipart.block.BlockMultipartContainer)
Actual block data value: 0 / 0x0 / 0b0000
Stacktrace:
at net.minecraft.world.World.func_72939_s(World.java:1804)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:620)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:709)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:240)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471)
at java.lang.Thread.run(Thread.java:748)

Please use the search functionality, this is reported multiple times.
Duplicate of #4374