Minecraft Forge 1.7.10 won't work?

So I downloaded Mo Creatures 1.8 because I thought 'ey new update why not get the better newer stuff' and it works just fine. But then I tried getting 1.7.10 because I realized most multiplayer servers are still 1.7.10, and even though I installed everything right every time I try to play singleplayer or multiplayer 1.7.10, the game crashes.

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