HELP!!!!! 1999 mustang weird start problem

[kardez]

I've got a 1999 Mustang with a strange electrical problem. Normally, the car starts fine ,but now the car absolutely does not try to start at all. The entire electrical system goes down and the only way to get it back is to disconnect and then reconnect the positive battery terminal. However, disconnecting/reconnecting the battery and then try to start the car again immediately, the car will refuse to start and the electrical system will again die. Does anyone have any ideas that might help? I imagine this might be something not to fool with myself and just take it in to an electrical shop, but that would be too costly for me right now unless i really have too. Any help would be greatly appreciated