Here is the log: http://paste.ubuntu.com/10740367/
It happens without Fastcraft too.
Help? Thanks!

This log...actually answers a lot of other questions. Thanks for reporting, looking into.

Fixed

It does..look at my modpack's issue ticket...
Really happy this issue is fixed already.
May I ask what build includes this fix?

It's currently only in development, but I'll have an official build released today :)

Okay, thanks @aidancbrady.
I'll wait.