This is really bizarre: I have imported numerous jpgs and am arduously creating a stop-motion-esque film. I see the perfectly-sized jpgs in my timeline, and yet, when I "publish and share" a full-quality video, strange crops appear that I haven't even added to the jpgs.
Attached are screen shots of timeline and quicktime showing the exact same jpg within the video, yet one is cropped.
From your thread, it appears that you are using Premiere Elements 12 Mac. Have you updated 12 to 12.1 yet using an opened project's Help Menu/Updates?
To your immediate issue, the important part of your situation that is missing is the description of the Publish+Share/Computer/QuickTime export settings...what did you select for Presets and did you go with default settings for the preset selected or customize the selected preset under its Advanced Button/Video Tab?
Please supply more details. Also
What is your player?
What is your project preset?
What are the pixel dimensions of the jpeg.