Comment 67 for bug 548631

I tried several solutions mention here. Even editing: .config/xfce4/xfconf/xfce-perchannel-xml/xfce4-keyboard-shortcuts.xml
and setting the write protection with the immutable flag:
sudo chattr +i .config/xfce4/xfconf/xfce-perchannel-xml/xfce4-keyboard-shortcuts.xml

Nothing seemed to solve the Problem. When I hit alt+F2, my xfrun4 won't come up. xfce4 keyboard manager was also unable to accept my changes and even removed my config entry when I hit alt+F2 for shortcut recording. I therefore assume that this configuration windows is broken.

Finally, I found a solution for me: when I hit alt+f2 in the gnome-terminal, it posted a capital P. Alt+F1 produced a capital Q.
So I assumed that my keybaord layout was broken.

So I went to "xfce4-keyboard-settings" ->keyboard layout tab (most right one) and removed my keyboard layout. After adding the same back again and relogin to xfce4, my keys did work.