Framerate and mouse sensitivity

So I recently got an alienware x51, with an Intel core i7 processor. I was browsing the internet without a single problem. I downloaded a game today, runs on java, and when I opened it everything was fine. It was until I actually out of the game menu and into a game when it started:

1. My frame rate decreased to 0 fps and 20 fps every now and then.

2. I would move my mouse 1 mm and I would be looking at the top of the screen, and then at the bottom.

I lowered the sensitivity of the game to the lowest possible, still the same issue. I downloaded Java, still the same issue. I plugged in a new mouse, still same issue, and I restarted the computer, but still the same issue. When I browse the internet then everything is fine and the sensitivity for the mouse is normal, but not when I play the game.

The game is not a game which requires an extreme gaming computer. In fact I was able to run the game on my old PC, which has an intel core i3 processor, perfectly fine.