with regedit , navigate to:
HKEY CURRENT USER\Software\Synaptics\SynTPEnh\UltraNavPS2 (note HKCU, not HKLM)Change "TrackPointMode" to dword:00002214 from the previous value of 00001214
Open the mouse properties and on the UltraNav tab, disable the TrackPoint by clearing it's check mark, click apply. With the keyboard, track pad or other pointing device, re-enable the TrackPoint and hit apply.
Your middle button should now function correctly.