I think I am getting to understand the Video Sequence Editor now but I see what seems like a bug with loading a DPX image. The image shows “wrapped around” so that about 15% of the right-hand side of the image is actually on the left. However, the very same image in TIFF format is framed correctly. Both images are 2048x1024 pixels in size. The problem occurs regardless of the project output dimensions (eg. 640x480, 1920x1080 or anything else).
Here are screen-caps showing the DPX (problem) and TIFF (ok).