Sorry, I think the site I was using for my avatar got infected. I didn't notice, since I'd been using it safely for a while, and my mac doesn't get viruses, so I don't have much in the way of alerts. I've changed the picture now, so the warning should be gone.
Another potential issue with hotlinking from the original site. I've known some site owners who took a dim, dim, view. When they found a hotlink to one of their images, they'd replace the image with something horrid, repulsive, and genuine guaranteed to cause disgust and revulsion on the person who's avatar or linked image has been linked to the .. customized... material. The
nicest thing the webmistress I knew used to replace a hotlinked avatar image to was PedoBear....
End result, safest thing is to save the image to PC, then upload to a photobucket (or similar) account. Saves bandwidth for the original site owner, saves you from potential issues if somethinghappens to source you're linking from.