I have a LG Flatron E2750v Monitor connected with a standard cord between the monitor In the center of the screen it reads: D-Sub out of range 68.5Khz/85Hz VGA Port or Power saving mode HDMI Port

SOURCE: LG Flatron monitor remains in Power Saving Mode

Sounds like an issue with a memory card or pci card not properly in place. Try opening up the sytem, then make sure each card is properly inputted in it's slot. This may cause the the monitor to show power saving mode especially if the memory is not properly placed.
Thanks

SOURCE: My LG Flatron L1511S 15 in. Flat turned into Power Saving mode when I plug in serial cable!

if the monitor showing powersaving mode, monitor is ok. It must be your CPU complaint.

SOURCE: Analog Out Of range (LG Flatron L1750T)

some games need high resolution. Monitor resolution not supporting for this game.
Powersaver mode showing when the main PCB of the monitor failed. check this link to get the service center info
http://www.lgservice.com/

SOURCE: LG Flatron LCD Power Saving Mode

Hi, September 2008 and still problems happening with the LG screens. Mine is a Flatron W1942T.
I hit the screen as suggested (my old mum was a great believer in " if it won't work kick it", this applied to anything electrical, tele, vacuum cleaner etc.,) and guess what? my old mum was right. The screen came on.
Hope this works if it happens again. I'd turned everything off because of an electrical/thunder storm. Won't do that again.
Joan

SOURCE: Power Saving Mode problem using the DVI input. VGA input Ok.

try the display on another computer, if the display does the same thing on another machine, then its definitely a problem in the display not in the computer drivers or bios.