Skipping after Encode - Increasing Source Default Framerate the Culprit?

So I’m encoding some home vids to Divx in Divx Author, and have noticed some slight stuttering in my final output files during what should be smooth motion. It’s not huge. Like the movie is still watchable, but it’s just not always looking as “fluid” as the source.

I should mention I’m doing quite a bit to the original source in an effort to increase quality of these movies and I’m pretty sure one of these tweaks is the problem.

Original Settings of Source File are:

Resolution: 640 X 480
Pixel Ratio: 1:1
Framerate: 23.976

My Changes and Final output settings are:

Resolution:720 x 480
Pixel Ratio 40:33
Framerate 29.97

(Among other things like Manually Increased Bitrate,
Slight Increase in Bitrate Control Mode for Speedier movie,
Insane Quality, 320 kbps MP3 sound)

Anyone notice what could be doing this? My encodes are double pass to Divx and that’s about all I can think of. Any light shed here would be cool