I was trying to make work one vagrant + selenium grid setup and faced with next problem :
Net::HTTPNotFound: No gems found matching "vagrant-vmware-fusion" "2.4.1" nil
After some googling i found a magical fix for it. Are you ready? Just try to install plugin one more time :) It actually worked for me and other people who were facing with this problem. Don't know if it's some bad server performance issue or some connectivity problems, but after Nth trial it actually downloads needed gem and installs plugin.