another update/boot problem

Current OS is 11.2 2.6.31.12-0.2 ATI HD4200 graphics card

Three evenings ago I updated to the current version. The following morning on boot up, the login screen disappeared. Grub seems to work fine and the system will boot in safe mode; however, it appears that Sax2 is malfunctioning-data incomplete in xorg.conf file Undefined screen ati…- and will not allow adjustments to the monitor.I have read the issues surrounding the Ati card but fail to understand why it worked well until the update. Is there a work around for boot up? I have considered upgrading to 11.3 but it appears that the Ati cards are not exactly compatible. Any help is appreciated. Thanks

Did you try reinstalling the ATI driver?

Yes, I installed the latest version from Ati -10.8… . I also tried nomodeset at the grub screen. Is it possible to undo the latest updates? Probably not without a previous backup.