I have been playing and having lots of fun with Compiz, with great results. But, when I boot up, the "cube" works and revolves, and shows my desktop background when spinning, but any windows that are open cannot be moved, and will not close. To "fix" this, I have been opening a konsole and:

compiz --replace ccp
This, after a few flickers seems to work ok. Having done this I saw that the konsole was still open. I tried all I could think of to close it (the running process) incuding ESC, ctrl-D, ctrl-x, :q ....
I then typed exit............
Screen went completely black, no way to do anything so I hard booted (crashed) the computer. Upon reboot...
Black screen, KDE tip o' the day, firefox restore session, BUT NO desktop or task bar or kicker or any controls at all... no way to issue commands etc ctrl-alt mouse still spun the cube, but only to more blackness. I eventually, by luck rather than any expertise did ctrl-alt-f2 to a ?? level 3 CLI ?? and typed KDE, This bought me back to a log in screen, I did
compiz --replace ccp
again, and .... phew all was well!
How do I get out of the compiz session in a terminal? (I just close the konsole now)
What is compiz --replace ccp actually doing?
Can I do the same thing on start-up somewhere?
When I do, although a small thing, can I get my background on to the spinning cube?
If I find myself in the black screen again, what is the best way to regain control?