Olá de novo,
Continuando a história.
Quando liguei o micro no dia seguinte a resolução tinha voltado para 800x600.
Aí fiz um monte de coisas e nada de resolver. Até que achei uma dica que solucionou o problema.
No lugar de usar o drive "vesa", que é genérico, usar o drive "fbdev", genérico também e que deu resolução de 1024x768.
Então, o arquivo xorg.conf fica assim
# This file was generated by dexconf, the Debian X Configuration tool, using
# values from the debconf database.
#
# Edit this file with caution, and see the xorg.conf manual page.
# (Type "man xorg.conf" at the shell prompt.)
#
# This file is automatically updated on xserver-xorg package upgrades *only*
# if it has not been modified since the last upgrade of the xserver-xorg
# package.
#
# Note that some configuration settings that could be done previously
# in this file, now are automatically configured by the server and settings
# here are ignored.
#
# If you have edited this file but would like it to be automatically updated
# again, run the following command:
# sudo dpkg-reconfigure -phigh xserver-xorg
Section "Device"
Identifier "Configured Video Device"
Driver "fbdev"
EndSection
Section "Monitor"
Identifier "Configured Monitor"
EndSection
Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
EndSection
A resolução fica só em 1024x768, mas como é a que eu uso, tudo bem.
Abraços
Flavio