i was finding a lot of noborder problems when compiz was started from the configuration editor as per alan's suggestion above.
i even found that sometimes, compiz wouldn't start this way and metacity was still loading... but still noborder problems.
i've put the configuration editor setting back to metacity, and now start compiz from pref/sessions.
this seems to have removed the noborder problems... so far at least.
(ps. not sure if this is because it reloads the window manager after start?)