ARTstor recently made a change in regards to downloading individual images. It used to be possible to download these without having an ARTstor account. That is no longer true. You must now have an account to download any images (individually or in groups to PowerPoint). Creating an account is easy; see these instructions on ARTstor’s help site. I recommend using the short form of your UW email address to create the account (e.g., firstname.lastname@example.org versus email@example.com).
When downloading individual images, you may see an applet window pop up. You must answer “Allow” to this in order to continue the download process. In order to not have to do it again during your current browser session, click the checkbox next to “Allow all applets…” If you accidentally click on the “Deny” button, you will have to completely close your browser and start over again.