If you create a dimension table with Material None before Feature Oregen (in an attempt to get normal Ore Generation), a single player world will crash with a null pointer exception, while servers will disconnect players whenever they perform an action which causes the server to access the dimension table's description.

Caused by: java.lang.NullPointerException
at mcjty.rftools.dimension.DimensionInformation.toBytes(DimensionInformation.java:64 ~[DimensionInformation.class:?]
at mcjty.rftools.dimension.network.PacketSyncDimensionInfo.toBytes(PacketSyncDimensionInfo.java:70) ~[PacketSyncDimensionInfo.class:?]
at cpw.mods.fml.common.network.simpleimpl.SimpleIndexedCodec.encodeInto(SimpleIndexedCodec.java:11) ~[SimpleIndexedCodec.class:git-Cauldron-MCPC-Plus-1.7.10-1.1307.06.218]
at cpw.mods.fml.common.network.simpleimpl.SimpleIndexedCodec.encodeInto(SimpleIndexedCodec.java:7) ~[SimpleIndexedCodec.class:git-Cauldron-MCPC-Plus-1.7.10-1.1307.06.218]
at cpw.mods.fml.common.network.FMLIndexedMessageToMessageCodec.encode(FMLIndexedMessageToMessageCodec.java:51) ~[FMLIndexedMessageToMessageCodec.class:git-Cauldron-MCPC-Plus-1.7.10-1.1307.06.218]
at io.netty.handler.codec.MessageToMessageCodec$1.encode(MessageToMessageC

After rebooting, the dimension table's description reads "Error: dimension information missing", or something similar.

The exact set of dimlets I used to produce this was:

Material None
Feature Oregen
Liquid None
Material None
Terrain Islands

By removing the first "Material None", I was able to craft the world without crashing.

I'll fix this but putting material none before feature oregen will not give you normal ore generation. Normal ore generation is done by default.

Ah actually in RFTools 2.90 this is already fixed.