Have any of you tried the vbetool utility? It works for me. My config is:
Toshiba Satellite M30-742
Nvidia Go 5200 card
Gentoo (kernel 2.6.14 with gentoo patchset)
AGPGART disabled in kernel, so using NVidia internel AGP.
vbetool (0.3 version)
vbetool dpms off - Switches off the screen
vbetool dpms on - Switches on the screen.
[ Screen switch off means complete switch off. Even the backlight turns off ]
vbetool works even though Nvidia driver is unable to "switch on" my screen (It can turn it off though).
I have tried vbetool from the virtual console as well as X. It works beautifully from both. No display corruption, nothing!!!
It should be trivial to add these vbetool commands to LID OPEN/CLOSE acpi events. My laptop apparently has a harware switch which turns off the display when I close the lid and switches it on when I open the lid. No acpi action scripts are needed. However I need vbetool for controlling this functionality from software. It is extremely useful for turning on the display after acpi suspend/resume.
Hope this helps.