No big calamity .. I will just use Internet Explorer for this task. If you can figure out why Firefox is refusing to co-operate that would be great but don't spend too much time nutting it out.
Well, thanks to your provided error message, I actually started to wonder how it could work (in IE). So, I found that with IE as a source, actually a normal copy command allows downloading such an image. This is all something possibly even Bill Gates hasn't seen before, because mystically this is a copy from the "Temporary Internet Files" to the destination (your album). And this source location already exists (with assigned temporary name) while the download (which under the hood *has* to take place) not even has been performed. This is only for Bill of course, and nothing for my ERP friend. And in the end ... this is nothing to copy, but something to download (officially).
So, I just have solved this into exactly that.
Oh, underway I found that the download command I use for it (which is dedicated for webclients), also allows "downloading from disks". Bwahahaha, so that's the other way around.
But I did both their own way anyway, and for Firefox too it should work now. Btw, I didn't test it (no Firefox here).
Have fun (0.9y-4),
Peter