I can confirm this change of behaviour, and it points to the KDE menue rather than wakeonlan.
Since I wrote 'wakeonlan' and the MAC-address into file, saved it under /usr/local/bin, the machine starts perfectly okay.
Therefore, it really looks like an inconsistency of KDE, and its behaviour of accepting parameters following a command.
I can confirm this change of behaviour, and it points to the KDE menue rather than wakeonlan.
Since I wrote 'wakeonlan' and the MAC-address into file, saved it under /usr/local/bin, the machine starts perfectly okay.
Therefore, it really looks like an inconsistency of KDE, and its behaviour of accepting parameters following a command.