Attached is a video example of the issue I am experiencing.
I'm new at using premier pro cs3 ( 3 weeks about )... so I'm no expert.
I'm curious if you know about a program called GSpot, which lets you get information about a source file or exported file...gives a lot of information about the specific nature of the video and audio. If you do a "screen capture" of the GSpot program with your source file, you can upload that screenshot here (should be 450 pixels or less in width to upload here ) and people would know what kind of file you are dealing with.
I have a sample 1080p file that was already converted to a MOV from RAW original, which I loaded into Premiere project of HD 720x480, and it looked good, previewed well (though cropped a lot, it was centered in the project monitor). Then I exported as a Quicktime (using H 264) and although the clip lost a lot of quality it exported OK and looks fair.
You might upload more specifics about what your source is and what you want to export as, and I'm sure people here can help.