Does the file exist in that location?
It would be an issue with your hosting provider if the file exists at that location but you can't view it.
It can't be a problem with your computer, and I see the problem too so it isn't a problem with your isp. Did you confirm that there is an image in that location.
Talk to your Hosting Provider support. Make it clear that a file exists at that location and send them the link to verify that they cannot browse to it either. I don't think they can pass the buck at that point.
Did this help? Tips are appreciated...
