imagecache populates its directory with the resized images as it creates them. It'll take the source images from /files/ and /files/ubercart_images/, process them, and put the results in /files/imagecache/preset/original file path. Check those imagecache directories to see if anything is in them. Also, try going to the Imagecache settings and "flushing" the presets. There might be a problem with an outdated cache.