Images in Signature File

[brendan]

I am unable to get an image to display in the signature file. I recently upgraded to Zimbra Desktop 2 and seem to have lost the ability. The image displays in the signature preference dialog, but not when I try to include the signature in an email. The text displays but not the image. I tried both adding the file and adding it via URL. Neither will display the image.
The image is in a publicly viewable web space.