I tried ProvoBob way to fix the file as well. I got error, I disabled Avast after reading Crimson's post and was able to run the mod pack with no problems. I tried to reboot the PC, and still failed and also downloaded all links. After I finished successfully installing mod pack I noticed notifications in Avast saying it had halted installing. Avast updated yesterday and I'm blaming the AV. :) Note: the troubleshooter in Window did not fix it, disabling AV did.