Ubuntu – Title bar disappears suddenly when Compiz is enabled

I am running Lubuntu 11.10 (LXDE based on Ubuntu 11.10). A few days ago, I installed the Macbuntu, but it isn't compatible with LXDE and so, I uninstalled it. And today I installed Compiz (I have tried to install Compiz in Lubuntu 11.10 before and everything goes well at that time). I tried to run Compiz with the command compiz --replace and everything seems ok. But after a short time (usually within three minutes), the title bar and taskbar disappeared suddenly, and I cannot open any program with the hot key (e.g. I usually open the terminal with Ctrl+Alt+T, but it doesn't work at that time).

I can do nothing but kill the Xorg and stop the Compiz in tty1. Now the system is fine without Compiz. But when I try to run Compiz, the horrible thing will happen again. and I noticed that, usually when I close a window, or change the configuration of Compiz, the title bar would disappear suddenly. I really don't know how I can fix it. Can anyone give a hand to me?

Another: i have run gtk-window-decorator --replace to start the window decoration, i got the error:

Failed to load theme "Ambiance": Failed to find a valid file for theme Ambiance


(gtk-window-decorator:3994): Wnck-WARNING **: Unhandled action type _OB_WM_ACTION_UNDECORATE