I noticed this when I tried to run a game (Starcraft) fullscreen using Wine.
The game runs nice, but after quitting I don't get back to the Desktop, but
instead get a black screen with some garbage graphics (white dots/lines).
I can move the mouse here, but do nothing else (no killing X11 using
<strg>-<alt>-<backspace> for example)

I think this affects return-from-fullscreen in more than the Wine case. While
I have seen fulslcreen apps where it worked fine (Zsnes for example), I also
found this very easy to reproduce example:

From GDM:
- <strg>-<alt>-<f1> drops to textmode
- <alt>-<f7> correctly gets back to X11/GDM => ok!

From an Xsession using _Metacity_:
- <strg>-<alt>-<f1> drops to textmode
- <alt>-<f7> correctly gets back to X11/GDM => ok!

From an Xsession using Compiz:
- <strg>-<alt>-<f1> drops to textmode
- <alt>-<f7> goes to the same black screen (with a few white pixels) as seen after Wine quits

The same thing can also be seen after starting/killing another Xserver (Xorg :1 for example)

All of this works fine without Compiz (see the GDM and Metacity examples). From within Metacity I also started a windowed OpenGL app and textmode<->X11 switching still worked, so I think this is not a driver bug... Any idea what I could try, or can this be fixed in a later version of Compiz? I will now fle another bug about a possible workaround (and the problems with that).

I am using the latest NVidia binary driver on a GF7950 and Ubuntu 7.04 (Xorg 7.2), latest Compiz from GIT.