I've been having an issue where every time I log on to my world, it crashes and this is the error within the crash-reports folder:

http://pastebin.com/PLC1dHcT

If this could be fixed as soon as possible that would be great because I would really like to start playing the FC3 "modpack".

Thanks,
AffectingHydra

Thanks cruck1000. That actually solved my problem.

Uninstall Optifine