I'm guessing you are referring to flickering lines at the bottom and/or top of the monitor?
I've noticed this in VHS movies I've recorded and pulled into MEP. It's because the recording window is slightly bigger than the source, I think. I've just ignored the flickering line (at the bottom for me) and MEP and noticed after burning a DVD, I didn't see the flickering line.
If the flicker does get reproduced in your final DVD, you may try playing with the "Image size and position..." option.
With your imported movie in Timeline mode, right-click on Track 1 (the video track) and choose "Image size and position..." You should be able to slightly reduce the size, which may work.
The "Video cleaning" dialogue has some interesting options, too, in the "TV picture" tab, but I've never used them so I don't know anything about how those options work.
If you're really referring to the effect that Tim suspected you're referring to, it's something I've also seen before many times when doing analog capturing. I'd typically see the flickering line at the very bottom of the captured image, mostly taking up a large fraction of the very last image line. I've seen this effect with different types of capture/TV hardware and different applications being used to perform the recording.
The reason why you don't have to worry about it much is probably because your TV will mostly cut off a bit on each side anyway (TV cropping). That's exactly what Tim describes: He doesn't use the option in the program to compensate for the TV cropping, so the offending part just gets cut off. So, in this case, the TV cropping is working for you. :-)