I was fly (or trying) at an almost hover, but then the motor slow down to a stop like my battery was dead but i have only been flying with a fresh pack for 2 mins. Then i put in the new pack, i can't arm it again. I'm using a Electro-Fusion 35. The servos, reciever, etc works and the light on the ESC responses to the throttle but it didn't make the usually beeping sound when you arm it and the motor doesn't move. Never happened before, been flying with this ESC for a while. Thanks, apprieciate it.

Sometimes when the brushes wear down on the motors and dont make good contact, the esc will not arm. Its not getting a complete circuit.

yeah, it's worn brush all right. One of the brushes is only like half the length of the other. That's what you get for being too lazy to clean it. I guess it's time to save some money for brushless.