Electrical Demons

Well other than my alarm or whatever is messing up I have another problem to add to the mixture. The other night me and my girlfriend was up town at the McDonalds and as we go to leave she says I'm cold. Since the car was already warmed up and everything I reach for the fan switch to turn it to 4. When I turn it KABAM!!! everything turns off. So we are sitting at a stop sign. I go to wave the cars behind me around me and a cop is behind me. He tells me to turn on my flashers and when I go to do that they won't turn on. Dun dun dunnnn. So we push the car down the road and to a gas station. I popped the hood to check the battery connects. Everythings tight. I knew it was because a few days prior I tightened up my ground to make sure it wasn't that causing my car alarm to go off. You know loose connection can cause pain. So when I check them they are tight. But my ground will spin on the post but won't come off....hmm weird. I'm beginning to wonder if I need a new battery. Why else would it my just tightened connections to still be loose. Or should I buy new connections. Also I have been looking at a grounding kit. If I bought this it would include the connection to the battery plus other grounds to help with electrical resistance. Well, what a post.