black desktop after exit of game

I installed 11.3 32 bit KDE on my system I had been running 11.0 32 for over a year.
nVidia card, AMD quad, 4 gig RAM …
Blender runs fine, fast and clean, when I exit, it takes a couple of seconds before I get control back.
If I play a game, Armagetron, IOQuake, FrozenBubble - when I exit I get my mouse pointer back in a few seconds, you see a couple of the windows open on the desktop for a brief second but all goes black. When you move the mouse pointer around the screen it changes as if it is going over an icon or window but it does not recover.
Anyone have any thoughts please?



Do you have desktop effects enabled?
If so, turn them off