What's wrong with my Airsoft gun? Please help!?

I ordered a JG G36C from Airsplat.com During test firing all of my bb's were hitting the ground less than 10 feet in front of me. VERY INACCURATE! I've owned this gun before in the past and it was the best gun I ever owned. But yesterday I attempted to play a game with it, and after the 3rd burst the gun stopped functioning completely. This is after fully charging the battery. I'm already in the return process with Airsplat, but I really would just like to know why it did this to me. And how I might be able to fix it if it happens again. Best answer get's 10 points!