Álvaro, Try this: log out of your KDE session, then execute mv ~/.kde4 ~/.kde4_old from a terminal, and then log back in to KDE. Check to see if the issue persists. If the issue is gone, then your KDE configuration was previously corrupted. If this is the case, just reconfigure your system, or try restoring important subdirectories of .kde4_old into .kde4. -Kerrick Staley
