First, make sure you have NEI, second, what version of IC2 are you running? And what other mods?
As to your error:
Code:
IC2 detected an ID conflict between your IC2.cfg and the map you are
trying to load.
Map: New World
Config section: block
Config entry: blockCable
Config value: 4054
Map value: 4078
Adjust your config to match the IDs used by the map or convert your
map to use the IDs specified in the config.
That's the part that's important. There's a block in your world that was created with the ID 4078, but at some point changed to 4054 and now it won't load it because of that. Find whatever ID is 4078 and change it to 4054 and it should work. For that ID. Since there's one ID confliction like this, there's almost certainly others.