Comment 56 for bug 160264

davidetkarine: When I switch between concurrent user sessions with Ctrl+Alt+F7/F9/etc. (changing virtual consoles) in Ubuntu, no problem whatsoever. White screen results in when the user session is being locked while switching (and that's what Fast User Switch applet is doing). See if you can simulate this type of behaviour on Mandriva. I believe that any screen updates on inactive graphics console will result in white screen when bringing it back to foreground (switching to it) later.