I can't play anything before 1.7.4

When i go to play any version of minecraft below 1.7.4, it loads up the green bar and then the loading bar goes blank and doesn't actually load up the game. I used to be able to play these versions but for some reason it crashed one time and hasn't worked since. I only say this because i can't use anything like forge and i would like to play some mods but because of this, 1.7.2 forge won't load up.