won't start, no electricity

[vin]

Question, Assuming the batttery is just fine, what could cause my diesel to go dead? Dead as in lights don't work, engine won't turn, nothing?
A breif history, 1980 300d, tried starting after sitting for a few months. Battery was to low to turn over fast enough to start. Neighbor hooked his truck up to jump start. Tried to start and starter got stuck, lights went out in dash with the engine still turning over. Had to disconnect negetive cable to stop. Since then, DEAD. I've looked at the cables and they seem fine. I feel it must be somthing really simple. Or at least I hope so. Any ideas? Thanks, Vin