Are you talking about scenes rendered as slo-mo in Vegas, or using the player's slo-mo features? Either way you could try increasing the bitrate of the mpeg2, but without the caliber of equipment and software they use commercially, you might not get much improvement if you're talking about the player's slo-mo function.

If you're talking about interlacing &/or telecine (depending on the source captured), you can try reversing the field order on the mpeg2 render settings.

For the captured portions that don't appear smooth, might be the codec you used to capture them or something related. Zoom into the timeline to see just what's happening, what the individual frames look like in your problem scenes. If you still have the original source, might try re-capturing just those portions using another codec or codec settings. Capturing analog video is still often a bit imprecise on a PC, and if there's a lot of motion or a pan, you can get a jerky effect that *might* be helped by a little blur or similar.

mike