I pressed something by accident, I think it was Fn + F11 (or some other key close to F11) and disabled my touchpad. How can I re-enable the touchpad?

The message I got was: http://wstaw.org/m/2013/08/01/plasma-desktopBa1943.png

try FN+F7 (diff hw may be diff)

see viewtopic.php?f=225&t=111360#p269515

To re-enable the touch pad, open ~/.kde/share/config/ktouchpadenablerrc with an editor and change it to
touchpadEnabled=true

try systemsettings -> input devices -> touchpad ->

Thank you, editing the configuration file worked!

touchpad configuration module from kde-apps.org as part of their default KDE installation.

Enable touchpad again :
Go to System settings - Input Devices - Touchpad and turn it back on there

On my particular machine the shortcut is Fn+F9, it is really annoying to me as it is immediately to the left of the mute button which is Fn+F10, when I accidentally press Fn+F9 it disables the touchpad, but pressing it again does not reenable it as it pops up with the exact same "Touchpad disabled" notification, hence the only solution is to log out first and log on again.