duster sparks from battery ground

I'll start by explaing the problems. Car turns over very slowly or not at all, replaced starter and battery, no change. Took battery out of trunk and mounted correctly with oem battery terminals under hood, no change. When the battery ground is connected to the car , small sparks fly. I am thinking I have a open connection somewhere, any advice where to start looking? Also my key is stuck in the ignition could it be related ? I have a new one to replace it just waiting to fix this issue first. Thanx