Everything that follows is nth. but the product of an error from my part:
As mgraesslin pointed to me I accidentally pressed the shortcut to enable window tiling (which seems to be about the only shortcut I failed to delete), right after upgrading, which made me jump to false conclusions.
If any admin would like to, feel free to delete the entire post and accept my apologies.
________________________________________________
Since the last update to kde 4.8.3
everytime I launch an application or switch to an already opened window a random (at least for me) and extremely annoying tiling of 2, 3 or more windows takes place.
Is this a new feature, and old feature that has been turned on by the update, or a bug?
Whatever it is, it has turned my desktop completely unusable!
Can anyone give me a clue before I switch to gnome?

Example:


More information: when I double click the title bar in order to maximize,
it maximizes vertically, then horizontally and finally both.
ergo: 6 clicks to get a maximized window, provided you have a title bar!

SOLVED:
Apparently, the upgrade turned on a (new?) feature in systemsettings: spiral tile (I assume).
(I was three seconds away from Unity).

You turned on window tiling. You can disable it using the shortcut alt+shift+f11

mgraesslin wrote:You turned on window tiling. You can disable it using the shortcut alt+shift+f11

I sistematically (manually) remove all shortcuts after installing, so either the update did it or my 4 year old son son has learned how to reassign shortcuts