Oh jeez. Stepping in here. You realize that you're messing with a mechanism that is fairly dangerous correct? Do some searches on this website and you'll read a lot of negative things about this.
When the cable unraveled, you may have tweaked the shaft slightly and everything is bound up. Be aware that all of the spring tension is now (somewhat) sitting all on the other cable. The drums are probably not aligned anymore (coil-wise) and it's completely cocked. And you're trying to mess with the spring that can seriously injure you. Whatever you do absolutely do not start loosening the bolts on the springs or the other drum.
You need to call a pro. They will come out and loosen and manually unwind both springs, then they will loosen each drum to pull the slack of the cables tight on each side, then they will re-wind the springs equally, then they will do final tweaking to make sure the door balances itself at a certain position, and your door will be back to normal. Your door, when it's in the down position, is when it has the MOST spring tension (most dangerous).
As stated before, if you're asking these types of questions, that means you really shouldn't be messing with these things. Even people with knowledge, shouldn't be messing with garage door springs. There's two types of work I don't do - roofing, and garage spring winding.