This week, one of the most critical bug left in our 2007 Spring release candidate was about the fglrx proprietary driver for ATI cards. It made the screen turn black when resetting an Xsession, making the system unusable locally (#29550).
Worse, during the first boot of a Mandriva One after installation, it made the first X session unusable...
To workaround this, we used the same workaround that had to be used in Mandriva 2007.1 for repeat logins with AIGLX, which is to restart the X server instead of resetting it. I've patched our DrakX libs so that harddrake and XFdrake set the correct options in kdm and gdm configuration files when the fglrx driver is used.
Maybe the 8.35.5 release of the fglrx driver would solve that, the changelog shows a bugfix for a similar issue, but we were to close from release to switched to a new fglrx driver.
Too bad we still need proprietary drivers for high-end ATI cards :-/