Updated xorg-x11-server packages that fix a bug are now available for Red Hat Enterprise Linux 6.
X.Org X11 is an open source implementation of the X Window System. It provides the basic low level functionality upon which full fledged graphical user interfaces such as GNOME and KDE are designed.
Prior to this update, when the X Window System was unable to detect a monitor and obtain valid extended display identification data (EDID), it set the default resolution limit to 800x600. Consequent to this, users of the "mga" driver for Matrox video cards were unable to select a screen resolution higher than 800x600. This update increases the default limit to 1024x768, allowing users of Matrox video cards to select this resolution as expected.
All users of xorg-x11-server are advised to upgrade to these updated packages, which resolve this issue.