Rescarnation

Hello! I'm using Forge and I have a few mods, Pixelmon being the newest addition (the other mods are compatible with Pixelmon), and Minecraft (it's version, 1.7.10; the mods are all the same version) won't seem to start. It starts with a black screen, then proceeds to the "Mojang" screen, before crashing. I need some help as to why... Please and thank you for your help!