Trying to import an image sequence of jpegs when they are imported into AE only the top left quarter of the image is being shown in the Composition window. The images haven't been scaled down it like the original image has been cut into 4 sections and only top left is showing. Scaling the image down doesn't reveal the rest of the image it just scales down the section I can see.
How big are your JPEGs, and what dimensions does AE show for your imported sequence? How big is your composition? Are you dropping the sequence directly into your composition or are you nesting one composition into another?
It is easier to destroy than to create.
More fun, too.