I get this crash: java.lang.NoClassDefFoundError: eureka/api/EurekaAPI

Full crash log:
http://pastebin.com/066MkqeX

I'm using Buildcraft Additions #124

The problem is that you use a version of BCA which is using the new Eureka. The new Version of Eureka is currently only available for testers. So what I recommend is downgrading BCA to build 111 or even to the latest stable on curse.

what version of Eureka have you installed?

Ah alright that might cause it, thanks for the help!

yep that's the issue here, the new eureka isn't done yet so no relase of that yet