Did you 'refresh' the web page it was supposed to be on? Sometimes, the browser keeps the old page and shows you that. Also, did you publish both the folder with the new image and the page it's supposed to be on?
I am guessing this is on a Sitebuilder site. If this doesn't work, then try deleting the image and adding a new image. Unfortunately you will need to set the size again, but this should fix it. This sometimes happens with the replace option.