Description of problem:

After leaving the server alone for some time and activating the
monitor's power saving mode, the screen is blank even after touching
the mouse or keyboard to recover from the power saving mode.  The
monitor's power lamp changes from orange to green so it seems the
power itself has recovered.

The screen image could be recovered by pressing Ctrl+Alt+Fn to switch
to another console and pressing Ctrl+Alt+F1 to switch back.  I have
attached the Xorg.0.log output.  The messages below are at almost near
the end of the file.

When the monitor enters power saving mode, the following lines are
appended to Xorg.0.log.
--------
(II) XGI(0): XGIDisplayPowerManagementSet(3)
XGISetDPMS(VESA_POWER_STATE = 0x400)...
XGI - No valid address of VBIOS ROM!
XGIPowerSaving()...Begin
Turn off DAC1...
Turn off DVO...
Turn on DAC2...
XGIPowerSaving()...End
--------

Then, by touching the mouse or keyboard.  The screen is still black.
--------
(II) XGI(0): XGIDisplayPowerManagementSet(0)
XGISetDPMS(VESA_POWER_STATE = 0x0)...
XGI - No valid address of VBIOS ROM!
--------

By switching to another virtual console by pressing Ctrl+Alt+F2.
--------
(II) XGI(0): vgaHWGetIOBase: hwp->IOBase is 0x03d0, hwp->PIOOffset is 0x2c80
Part2 0 = ff (II) XGI(0): vgaHWGetIOBase: hwp->IOBase is 0x03d0, hwp->PIOOffset
is 0x2c80
--------

By Switching back by Ctrl+Alt+F1.  Image displayed as before.
--------
(II) XGI(0): vgaHWGetIOBase: hwp->IOBase is 0x03d0, hwp->PIOOffset is 0x2c80
(II) XGI(0): vgaHWGetIOBase: hwp->IOBase is 0x03d0, hwp->PIOOffset is 0x2c80
(II) XGI(0): Setting a standard mode 0x64
Part2 0 = ff XGISetDPMS(VESA_POWER_STATE = 0x0)...
XGI - No valid address of VBIOS ROM!
AdjustFrame 0
(II) AT Translated Set 2 keyboard: Device reopened after 1 attempts.
(II) PS/2 Logitech Mouse: Device reopened after 1 attempts.
(II) Power Button: Device reopened after 1 attempts.
(II) Power Button: Device reopened after 1 attempts.
(II) Macintosh mouse button emulation: Device reopened after 1 attempts.
--------

Version-Release number of selected component (if applicable):
xorg-x11-drivers-7.3-13.3.el6

see bug https://bugzilla.redhat.com/show_bug.cgi?id=631738 for details