I remember I had to do the same thing, but i didn't get any errors.
I'd recommend deleting the twilight forest zip (or cutting it out if you want to back it up or whatever) then get a new one and place it in there after removing the old one.
Ok. So apparently I should NOT mess with mods. My current world is destroyed. I came back on and all my machines are gone. There are shadows where they used to be. Anything relating RP2,IC2,SC,TF is gone. And that was just a quick check. Not sure if it's possibly to get my stuff back but if not and I need to start over, then I really want to get this working so I can join the server.