Did both. Though I did find one problem: I was accidently using a version of Forge made for MC 1.4.5. So I switched it out for 6.3.0.378 which was for 1.4. However, the game still blackscreens. I was really hoping (there's that word again) that it was that simple of a problem, but it's not. I've deleted and reinstalled the mod, deleted and redownloaded the Forge libraries, and just plain deleted everything and started over several times. I've been on this for hours.
Is there nothing in the error log that points to a solution? Mods don't just decide to not work for one guy of their own volition.
EDIT: Decided to try a different mod. Dropped Buildcraft into the folder, but I got the same errors (NoClassDefFoundError); just substitute "Buildcraft" for "IC2." So somehow, Forge doesn't know the mods folder exists?I cannot wrap my head around this, but that may be because it's 5 AM.