After today's KDE 4.5.2 update (not sure which component is to blame), mailto links no longer worked in firefox or chromium-browser. I use kmail for mail. firefox did nothing (not even an error message) when clicking a mailto link. I was able to fix it by installing gnome-control-center and setting the GNOME preferred mail client to kmail. I'm fairly certain that those links used to work just fine before this update, but not completely sure as I use firefox quite rarely these days on this box. I haven't been able to get mailto links working again in chromium-browser, and I use it a lot more than firefox so this is quite annoying. It displays an error dialog when clicking such a link saying | Could not start process Unable to create io-slave: | klauncher said: Error loading 'kmailservice %u'.
Re: chromium: hmm... kmailservice is part of kdelibs3 , not sure how/why that is being envoked here.
FWIW, $ rpm -qf /usr/libexec/kde4/kmailservice kdelibs-4.5.2-8.fc13.x86_64 $ rpm -q kdelibs3 package kdelibs3 is not installed
BTW mailto links are also broken in konqueror just like they're in chromium, the error dialog boxes are exactly the same.
I can no longer reproduce this so I suppose it was fixed in 4.5.3-1.