Crew Craft is a fun modpack that gives you a taste of the things you can do outside of vanilla minecraft. Crew Craft features mods such as twilight forest, railcraft, bibliocraft, and more! So if you wanna have some fun with exposives come join Crew Craft!
having trouble ? with the modpack or any modpack make sure you are on java 7 because most mods are at java 7
more informantion about the java bussness link here http://www.technicpack.net/article/view/concurrentmodificationexception-in-java-18020.89