Apple seems to have solved the problem. The images that were in the upload process yesterday, this morning were already uploaded and I've been able to send my application for review.

Same Issue here. I'm loading my screenshots to the App Store, as I always do, and they seem to be loaded Ok. I can see the preview, but when I click on submit to revision the images dissapear and they show a Cloud on a greybackground, and I get the error warning.  "There are still screenshot uploads in". It seems to be an Apple side problem, let's have a coffee and wait a for a while.