5.4-RELEASE: mouse won't work (suspect KVM switch)

[Robert S]

I've just installed the latest 5.4-RELEASE on a PC using a kvm switch.
 I am completely unable to get the mouse to work.

The switch is a no-name one with two ports (in a metal case!!).  It's
been fine up until now, though I don't know if I've used FBSD on it.

When I (re)start the mouse daemon, with /dev/psm0 as the mouse port I get

# /etc/rc.d/moused restart
moused not running?
Starting moused:moused: unable to open /dev/psm0: No such file or directory
.
If I select /dev/sysmouse (which has usually worked in the past - in
/etc/rc.conf), it starts with no error messages, but there is no mouse
cursor on the console.  If I try to start X, there are no errors, and
the mouse is present, but does not move.

My mouse is a Microsoft Wheel Mouse Optical USB and PS/2 compatible.

If its of any help, here's the output of uname -a:
 $ uname -a
FreeBSD freebsd.mydomain.com.au 5.4-RELEASE FreeBSD 5.4-RELEASE #0:
Sun May  8 10:21:06 UTC 2005    
root at harlow.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386

Can anybody help me out of this predicament?  I realise that KVM
switches can be tricky beasts.