Display / "Overlay" problem (metacity related?) in 4.5 beta

Hm sometimes i have "overlay" problems, if i open a menu, in different gnome (or kde) apps (like the gnome main menu, abrowser, konversation, terminal etc.) a part of the menu still stays on screen.

Seems to be related to metacity or to my old ati radeon 9200 64mb (and/or bios).
To fix that "overlay issue" temporarily i have to: metacity-message restart

Note: I enabled metacity shadows somehow (don't remember atm how lol) back in taranis. and i upgraded to slaine beta from taranis.

Screenshot: http://rbose.org/wiki/images/b/b4/Trisquel4.5beta_display_bug.png