Version: (using Devel) Installed from: Compiled sources Originally had my jpeg attachment viewing set to gwenview, which worked great. In System Settings, set the Web Browser to Firefox, and now I get an error message about trying to view "file://" types when I click on a jpeg attachment. Ugh.
Fortunately, after changing the default browser to firefox, in svn trunk revision 896766, when I click in the attached images (png, jpg), I get the offer to save, view with gwenview or cancel.
Works here to. Using kmail 1.11.1 from kubuntu packages.
Bug seems fixed. Good work.