"OK, it took me a LONG time to find out how to resize a picture on a Mac to post it here (open it in Preview, open the Tools menu, and choose 480 x 640)."
I'm not sure how to open a picture in preview that's already been downloaded to
iPhoto, however, I found an easy way to resize photos.
While viewing the picture in iPhoto, click on "Share", then "Email", and in the bottom right corner, there's a drop down box, choose "medium" (size), and "Send".
I found that when I email it to myself, I save it, then choose it to upload to QB, and the size is perfect for uploading.
Hope this helps.