So I was playing Hexxit and I left, a little while later I went to get back on to join a server I made to play Hexxit with my friends on, yet when I tried to join it said "Bad Login". Now I don't know what thats about but then I decided to restart Hexxit, but when I tried to start it up it wouldn't work (And no, its not saying anything like minecraft has failed to start up, minecraft doesn't even appear.) So I thought re-installing the modpack would work, but now its not allowing me to install it again, what should I do?