After I installed FreeBSD 6.2, I found out that my wheeled Microsoft Mouse does not support scrolling any more.
Under FreeBSD 6.1, all I needed to do to enable mouse scrolling was changing the InputDevice section in /etc/X11/xorg.conf from using device /dev/sysmouse to /dev/psm0 and changing the Protocol type to auto (see below), as suggested by various resources on the internet.
Section "InputDevice" Identifier "Mouse1"
Option "Protocol" "auto"
Option "Device" "/dev/psm0" Option "Buttons" "5"
Option "ZAxisMapping" "4 5"
But after I installed 6.2, using this setting would either lead to mouse scrolling not enabled or the complaining of /dev/psm0 being busy. Some resources had suggested changing the ZAxisMapping to 3 4 instead of 4 5 but it didn’t work for me.
After some testing it seems that the setting in /etc/rc.conf seemed to have somehow interfered with the setting in xorg.conf. I must have chosen to enable mouse in console sessions during the setup. By commenting out the following two lines in rc.conf the scroll wheel seemed to work.