Deleted version of image (same name) still showing up in posts

Hi,

I have a self-hosted WP blog on bluehost.com (edwinli.com/ux/), running a network, and using the Twenty Twelve theme.

For two of my pages (full-width template),

• http://edwinli.com/ux/portfolio/
• http://edwinli.com/ux/portfolio/process/

I wanted to have an image appear above the title of the page, as in a post that has a featured image. I learned from a support thread here that that’s not possible currently (http://wordpress.org/support/topic/featured-image-for-pages?replies=6).

I’d created an image that was 960px x 290px.

So then I went with an workaround alternative, by adding that same picture full-sized at the top of the pages (to appear under the page title).

But I wanted to re-edit the image (bringing some of the elements in away from the edges of the image). I edited the image on my computer, deleted the first one from my WP media library, then re-uploaded the image, using the same filename.

Then I added them back to the two pages.

But when I look at the pages in my browsers now (laptop, tablet, smartphone), what I see on those pages is the old image.

When I click on the image on that page, I get the new image at this URL: http://i1.wp.com/edwinli.com/ux/wp-content/uploads/sites/2/2013/06/portfolio-header-image-01.jpg

When I click to Edit the image from the Media Library, I see the correct, new image on that Edit page. But when I copy and paste the permalink on that page to see the image (http://edwinli.com/ux/portfolio/portfolio-header-image-01/), I see an attachment page, but it shows the old image.

When I click on that old image on that attachment page, I get the new image (same URL as the previous paragraph).

I lost track of how I got to it, but I managed to get to this URL, which shows the old image: http://i1.wp.com/edwinli.com/ux/wp-content/uploads/sites/2/2013/06/portfolio-header-image-01.jpg?fit=960%2C960

I don’t know much about how the system works, but it seems as if there is some sort of server-side caching going on that is not being properly updated with the new image. Could it be that the system is confused by the fact that the newly uploaded filename is the same as the old one that I’d deleted?

What can I do to flush the old image from the system? I’d already used “Delete Permanently” on that old image before uploading the new one…

Thanks in advance!