What is the format of the source AVI file?
make sure that that no corection filters have been applied to the clip and uou are working with a clean AVI file.
I suggest that you begin with a test that involves a short portion of the entire clip (set the work area to about 5 minutes within the time line)and begin with the DV template for NTSC Progressive which should default to a Max bit rate of ~7Mb and quality of 4 and with a 29.97 frame rate. If that looks normal to you, that should indicate either the 24P or other features of your the template that you used are not compatible with the source AVI file or they have been mis-adjusted. If you get the results you were looking for in the test, then stick with the standard templates that meet your requirements based on the test. For every change you make to the standard template, run an additional test to be certain that no change have introduced the incompatibility.