Dell Latitude D630 Touchpad

I have a Dell Latitude D630 running Windows 7 that just recently developed touchpad and button issues.  Without any changes in drivers/software, the left touchpad button, left pointer stick button, and the tap feature of the touchpad all stopped working.  The corresponding right buttons work fine as does the mouse movement via touchpad and pointer stick.  Swapping the button assignments (left click to the right button, and vice-versa) shows that the buttons themselves are not being detected.

I have since attempted several reboots, checked to make sure that the mouse options are correctly set to enable these buttons/tap feature correctly, and uninstalled/reinstalled several touchpad driver versions.  The ones provided on the Dell Latitude D630 page were the ones I was originally using, and I have also tried ones directly from Synaptics, Alps, and ones from Dell for one of the Windows 7 Latitude models.  Interestingly, the Alps drivers re-enable the left pointer stick button, but not the tap or left touchpad button, suggesting that this is still a software issue not a hardware issue.  The others make no change in the behavior.  Any help would be appreciated with this issue, thanks.