The Z-buffer on integrated cards often becomes confused which leads to
surfaces that should be hidden appearing (and obstructing other surfaces).
This problem seems to have been around since at least Mesa 6.4.2 and is
still here in Mesa 7.0.3. A screenshot showing the problem can be found on
https://bugzilla.novell.com/attachment.cgi?id=115354 . The problem is
highly reproducible on openSUSE 10.3 and Ubuntu 8.04 .
It is probably already reported as
https://bugzilla.novell.com/show_bug.cgi?id=239188#c17 suggested addressing
it on the DRI mailing list.
Sitsofe | http://sucs.org/~sits/