I deleted all of the IC2 api folders from each of the mods (except of IC2, obviously) and the problem persists.
I found and deleted the IC2 api folder form the compactsolars, forestry, and railcraft mods. The mods I have installed are Millenaire, ReiMinimap, AdvancedMachines, buildcraft, compactsolars, forestry, IC2, Railcraft, Steve's Carts, and minecraftforge.
Any help would be appreciated.