E-PL1 choppy video

My apartment is next to a railroad track. I tried using my new E-PL1 video to record a train passing by. With the zoom lens, each car filled the screen. The camera was set on "P" mode and IS setting #1. When playing back on my HD TV - using an HDMI cable - the images of train cars passing by was so choppy and staggard that I could not read words on the sides of the train cars. Thinking the problem might be IS, I disabled it and used the video setting for the next train. But I had the same problem.

Can anyone help me here? Must I assume the camera is not capable of recording subjects moving fast from side to side, or is there a way to set the camera to get clear video images of such subjects?

Note: I tried the same thing with a (much cheaper) Flip video camera and it worked fine - all of the moving train cars appear clear and sharp.

Thanks for listening....