Version: KDE 4.0.80 (using Devel) OS: Linux I clicked on a mailto link in the Konqueror, and KMail Composer opened. Then an error occured: Could not start process Unable to create io-slave: klauncher said: Unknown protocol ''. . E-mail adress wasn't copied to To: field.
I can't reproduce this, clicking a mailto link in Konqueror works fine for me. Maybe your installation has a problem or you're not using the lastest version?