premiere exported movie runs choppy?

[Gravija]

i have edited up a simple clip editing the halo nvidia promo video (jsut changing the sound) for premiere and after i export it, the frame runs really choppy and like fades with a bubbly water sort of effect into something about 7 seconds later

also, i noticed while editing that if i make it run, then the video plays REALLY fast and choppy while the audio runs at the same rate, i have made sure that the audio and the video are the same length as they should be (100% of normal speed)

why does this happen?

thanks