Oh look, another mod that breaks the game by attempting to introduce christmas festivities.

When the special christmas-themed "oil" starts or ends, you have to restart your client and your server. If you don't do this, you'll get a "fatally missing registry entries" error on join.

Steps to reproduce:

• Start your Minecraft server before december 25th
• Try to join on december 25th or 26th
• Get a "Fatally missing registry entries" error on join.

Same thing happens if your MC server started during christmas and you try to join afterwards.

Can you please post the log. Thanks!

That's extremely strange, as buildcraft only changes:

• The colours of BC fluids.
• Turns all of the gasses into liquids (a single boolean variable).
• The language values of certain fluids, blocks, and items.

Personally I suspect another mod uses the "gaseous" property of fluids and registers things using that, rather than buildcraft itself being the sole cause of crashing. However there's very little we can do without a log file.