SOLVED
I recreated the modpack.jar and it all worked.
Ok, so I just got my modpack up and running (Link: http://www.technicpack.net/modpack/details/not-vanilla-pack.1169) and it was all running fine, I had heaps of mods on it, I was playing it with friends, but then I removed the mod tree capitator, now whenever anyone tries to update the pack it downloads and gets stuck at 1% Timber!(1.4.6).zip..., I tried removing Timber, then I got stuck at thaumcraft. Please help, I can't play my modpack anymore and I don't want to have to start over...
I have tried clearing the directory for the pack, removing it and adding it, removing the mods it gets stuck on and trying it on multiple computers, none of this makes any difference.