catched this time to time. and this is compiz bug, cos im tested it. opened htop and started to kill processes till square dissapear.and this square gone after killing compiz process. compiz restarted without this white spot. and some other addition - sometimes this square takes almoust all desktop (like window). mostly catched after switching desktops with vlc *show on all desktop* option (but maybe this is justaccidentaly)
ubuntu 12.04 i386
unity 5.8 (with all latest updates on april 6) and catched from unity 5.4
intel x4500mhd
catched this time to time. and this is compiz bug, cos im tested it. opened htop and started to kill processes till square dissapear.and this square gone after killing compiz process. compiz restarted without this white spot. and some other addition - sometimes this square takes almoust all desktop (like window). mostly catched after switching desktops with vlc *show on all desktop* option (but maybe this is justaccidentaly)
ubuntu 12.04 i386
unity 5.8 (with all latest updates on april 6) and catched from unity 5.4
intel x4500mhd