This course gets images from various sites on the Web: the Art History image server (InSitu); Perseus; and an image folder on the Learn@UW site for this course. All require authentication of some kind or other, and this can be problematic, as you've seen in class.
To see images on the Learn@UW site, such as this one, log in first to Learn@UW with your UW netID and password (bbadger, yourpassword), then go back to this course. The system should remember you for a while at least.
As of Jan. 2008, the authentication procedure for InSitu seems to be having difficulties. If you're at home, or on campus using the wireless network, try establishing a connection with WiscVPN (you'll have to download the client software). This is a pain, but it works for me.
Images coming from Perseus are often slow, but they usually work. If they don't, try again.
If you have trouble please let me know just what image you're trying to see, where you are, and what happens when it fails.