just my own observations about my setup,
and how I eventually understood the reason VNC was blank after a
wakeonlan (wol) LAN wakeup, producing a dark screen
I call this "VNC blindness"
no miracle required to cure it, just doggedness
Dell Optiplex GS620/XP SP 2
the basic problem seemed to be hardware related:
the PC waking up from a suspend (S1 mode) does not power the graphics card and so VNC would always be blank.
the PC waking up from a hibernate (S3 mode) does power the graphics card and so VNC would always work
VNC sees the display!
Solution, the following always works:
set the BIOS to S3 mode
enabled Hibernate in the control panel "power options" "Hibernate" tab
turned off the screen saver (none)
set power options as follows:
"turn off monitor" to "never"
"turn off hard drive" to "never"
"system suspend" to "never"
"system Hibernate" to 1 hour (or whatever)
now when waking the PC with wol, the wake-up from S3
also powers the graphic card.
I am still trying to understand the complex relationships between
the power options on XP/SP2
"turn off monitor"
"turn off hard drive"
its still above my pay grade.