Modpack Crash issue

[Asip]

Hello I recently created custom modpack for me and a few real life friends however it works perfectly fine for me, even when I'm using the same exact build as my friend who is playing on a mac(Which I believe is the issue because I believe macs are the source of all evil in this world and they must be purged...), anyway this is his crash report I got from going into teamviewer on his computer. http://pastebin.com/4gidCcYQ

[ruben654]

You have 2 items which try to use the same itemids