indeed, it seems that it's a design desicion rather than a bug http://bugzilla.gnome.org/show_bug.cgi?id=515907 added RGBA to system monitor so it can use the transparency capabilities of the Murrine GTK+ theme and yep it's only showed with a composite manager in this case compiz, you can probably also see it with metacity with the composite manager enabled, not a bug but a design desicion.
** Changed in: compiz (Ubuntu) Status: Confirmed => Invalid -- gnome-system-monitor window is semi-transparent when using compiz https://bugs.launchpad.net/bugs/274461 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs