Update: for (easier) instructions for Ubuntu Maverick/10.10 and later, click here.
Another Ubuntu release, another set of X.org shakeups.
Some things in X changed in Lucid (xorg 1:7.5+5 and higher), breaking existing Thinkpad TrackPoint scrolling configurations that modify files in /etc/hal/fdi/policy (like those you may have seen in this previous post). You can use gpointing-device-settings to apply the same policy, but I found that even that stops working after a suspend/resume cycle.
Samson Yeung pointed out to me the following fix which can be applied on Ubuntu Lucid/10.04:
Create a new file /usr/lib/X11/xorg.conf.d/20-thinkpad.conf with the following contents (on Ubuntu Maverick/10.10 and later, save the file to /usr/share/X11/xorg.conf.d/20-thinkpad.conf instead):
Section "InputClass" Identifier "Trackpoint Wheel Emulation" MatchProduct "TrackPoint" MatchDevicePath "/dev/input/event*" Driver "evdev" Option "EmulateWheel" "true" Option "EmulateWheelButton" "2" Option "Emulate3Buttons" "false" Option "XAxisMapping" "6 7" Option "YAxisMapping" "4 5" EndSection
Then restart X.
The configuration above works for both Thinkpad laptops with TrackPoints and the Thinkpad TrackPoint keyboard.
Source: instructions derived from these instructions by Samson Yeung. Thanks, Samson!