Comment 4 for bug 580131

I have a similar problem:
 * the KDE desktop is not showing icons any more (but the are there, I can click them)
 * I get "The process for the file protocol died unexpectedly" on every attempt to open File dialogue or tab in Dolphin
 * the .xsession-errors is *full* of these lines:
plasma-desktop(2833): Failed to lock file "/var/tmp/kdecache-dusty/kpc/kde-icon-cache.lock" , last result = 1
plasma-desktop(2833): Failed to lock file "/var/tmp/kdecache-dusty/kpc/plasma_theme_default.lock" , last result = 2
plasma-desktop(2833) KIO::SlavePrivate::SlavePrivate: Connection server not listening, could not connect
kdeinit4: preparing to launch /usr/lib/kde4/kio_file.so
kio_file(29752)/kio (KIOConnection) KIO::Connection::connectToRemote: Unknown requested KIO::Connection protocol=' "" ' ( "" )

This happens consistently, after a few hours of use of the desktop.