Load images from server on localhost, then upload them?

I wont bore you with the complicated background, but I have a problem, and I think Flash can solve it!

An application passes a list of URLs to images to my script. I need to then get these images onto my server. The problem is that the images are being served on a server on the users computer.

I was initially going to do this with PHP, and just pull the files that way, but I ran into a problem when I realised that the server wont accept incoming connections.

I then turned to Javascript, but I can’t load things from http://localhost/ because of XSS protection.

My last resort is Flash! I basically need to provide the URL of an image to the flash movie, and have it grab that image then upload it.

i.e.:
I call movie.swf?url=http://localhost:40000/images/DSC200.jpg, which then pulls that image into the flash movie and uploads it to my server.

Is this actually possible?