The code I am running :

bush = GameRegistry.registerBlock(new BlockBushes().func_149663_c(Strings.BUSH_NAME), ItemBlockMulti.class, Strings.BUSH_NAME, Reference.MOD_ID, BUSH_TYPES);

ItemBlockMulti extends ItemBlockWithMetadata, with a constructor using (Block, ArrayList<String>), and BUSH_TYPES is of type ArrayList<String>, by the way.

It doesn't matter actually, if commented out, it crashes the same with the next block registration attempt.

 

The debug reached there:

 

It looks like the ItemBlock couldn't get the same id as its Block, for some reason ?

Note that the block id reached exactly 256, which may be related to that. (The previous block used blockId=255, and loaded correctly with itemId = 255)

Looking into itemRegistry didn't give me anything.

1.7.2 does not use IDs anymore, instead the use the Block/Item itself.

If it wasn't obvious from this screenshot, that GameData is from the cpw.mods.fml.common.registry package.

I am not using IDs. FML is.

Make sure you update to the latest Forge version. It shouldn't give you 256 as a ID in the block list, if it does i'll have to poke cpw about it.

Confirmed to be fixed in later Forge.

Thanks Lex