Why startx files on /dev/agpgart when xf86cfg runs? (XFree86 4.3 for Woody)

[Daniel Barclay <daniel@fgm.com>]

If xf86cfg can successfully run the X server, why would running X
with startx die with an error saying:

  (EE) GARTInit: Unabled to open /dev/agpgart (No such device)
  (WW) I810(0): /dev/agpgart is either not available, or no memory is available
         for allocation.  Using pre-allocated memory only.

?

This with the XFree86 4.3 backport to Woody, kernel 2.4.18, and an
Intel 845G/GL graphics controller.


Thanks,
Daniel