If your window title bar is gone. or you have messed the compiz in any other way in Ubuntu. Just open up a terminal and enter the following command:
Then Logout and Login back.
Edit:
As commented by zwergnase, the above command should also be followed by:
gconftool-2 --recursive-unset /apps/compiz-1
Then Logout and Login back.
Edit:
As commented by zwergnase, the above command should also be followed by:
gconftool-2 --recursive-unset /apps/compizconfig-1