si fatto...ho trovato questo su google: http://www.intilinux.com/howto/409/u...ede-video-ati/

qui dice verso la fine, che quando compare quel messaggio, bisogna aggiungere una stringa e un file. io l'ho aggiunta e digitando compiz --replace da terminale, mi dice:



codice:
bovy@bovy-desktop:~$ compiz –replace -v &
[1] 6212
bovy@bovy-desktop:~$ Checking for Xgl: not present. 
Blacklisted PCIID '1002:4153' found 
SKIP_CHECKS is yes, so continuing despite problems.
Checking for texture_from_pixmap: not present. 
Trying again with indirect rendering:
Checking for texture_from_pixmap: present. 
Checking for non power of two support: present. 
Checking for Composite extension: present. 
Comparing resolution (1024x768) to maximum 3D texture size (2048): Passed.
Checking for nVidia: not present. 
Checking for FBConfig: present. 
Checking for Xgl: not present. 
Starting gtk-window-decorator
/usr/bin/compiz.real (core) - Warn: Unknown option '-v'

/usr/bin/compiz.real (core) - Error: Couldn't load plugin '–replace'