Observation: After logging out, closing FF, reopening FF and revisiting this topic again, all imgur images are broken. (The first image is not hosted at imgur and is therefore working)
Freshly opened FF, not logged in, visiting this topic: All images in the first posting are working
Freshly opened FF, logged in, visiting this topic: Last image in the first posting is not working
Chrome
Freshly opened Chrome, not logged in, visiting this topic: Last image in the first posting is not working
Freshly opened Chrome, logged in, visiting this topic: Last image in the first posting is not working
This is repeatable.
EDIT: Above results are for internet access via cable. Just to rule out that it is a connection problem, I crosschecked via mobile phone tethering: same result.