Which nvidia driver did you install?
What does sysctl hw.nvidia.cards.0.model tells you?
What does sysctl hw.nvidia.cards.0.model tells you?
$ gconftool-2 --get /apps/compiz/general/allscreens/options/active_plugins
[[B]core,decoration,move,regex,resize,vpswitch,cube,rotate,switcher,cubeaddon[/B]]
$
adamk said:Is the window decoration plugin enabled?