I drove home from work and parked, didn't notice anything funny. When i went back out later to leave, the car wouldn't start. I just bought this car used (1999 Accord V6) and had had a diagnostic on the car done. They had told me the battery failed the load test but that the ignition system was fine. So i figured that was what it was and i went and got a new battery, which i installed. The car is doing the exact same thing. Lights come on, but no noise, no cranking (i can here a little buzz). If i have the lights on when i try to start it, the lights do not dim. The clamp on the negative side is loose, but touching. There was some corrosion in the negative clamp, so i cleaned that off with baking soda, lime and water, but I still can't unscrew the bolt to tighten it. Could it just be that the clamp isn't tight? I checked the fuses and they look fine, thought the battery fuse is missing the clear plastic cap/top that the rest of the fuses had. But the copper itself was intact.

Can anyone offer any suggestions? Should replace the entire negative/grounding cable and clamp since i can't get the screw off?