trouble reconfiguring xserver-xorg

[Haines Brown <haines@histomat.net>]

Startx on a jessie desktop machine goes to a VESA display instead of the
higher resolution supported by my video card.

In Xorg log is the error:

  (EE) NOUVEAU(0): [COPY] failed to allocate class

  I searched on line for what this means without luck. Only a hint that
  it might be a harmless errpr. Anyone know? 

I decided to reconfigure xserver-xorg

  # dpkg-reconfigure -phigh xserver-xorg

  This only returned me to the # prompt without asking any
  questions. Should it not be asking questions even if the nouveau
  driver does not allocate class?