I am reposting this issue from the Feed-The-Beast support forums. The Post can be found at http://forum.feed-the-beast.com/threads/fml-found-discrepancies-buildcraft-and-railcraft.19696/

Basically what happens is if the server and the client are using two different languages (Turkish and English in this post) there is an error. Uploading the language pack from Microsoft to make the client match the server resolves this issue. I thought you might want to know.

Thanks for the wonderful mod.

I have also posted this issue over at Buildcraft.

(I'm the same user here and on FTB forums)

Config mismatch, sync your configs.

How is a ID mismatch resolved completely by changing the language of the client?