http://gonzalo.gnome-db.org/moonlight/novell-moonlight-3.99.0.3-i586.xpi If you browse there you with kpartsplugin installed it will open up in ark instead of the addons installer. I was able to install it by disabling the kparts plugin first. This seems like an upstream problem but I could not find a way to report bugs through the HOMEPAGE linked. Maybe you can relay it there if you agree with the assessment?
Fixed in kpartsplugin-20110823-r1