This appears to be fixed in the current packages. gnome-print-manager still creates the URL without the trailing slash, but it seems that CUPS now does the right thing and successfully prints without it.
-- Dapper (updated today) -- cupsys will not use a jetdirect port other than 9100 https://launchpad.net/bugs/28405 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
