Fatal server error - cannot open mouse

[Steve Merrifield <sjm@livewire.ee.latrobe.edu.au>]

Hi all,

I have a problem starting X. It gives the following error:

Fatal server error:
Cannot open mouse (Operation not supported by device)

This is the relevant section from /etc/X11/XF86Config:

Section "Pointer"
   Protocol	"Microsoft"
   Device	"/dev/ttyS0"
   ...
   ...
EndSection

The mouse is definately attached to /dev/ttyS0, and works okay, because
I have gpm installed, and that uses ttyS0 with no problems. Also, XF86Setup
and xvidtune both work fine, but startx does not :(

Any ideas?
Steve