Thank you jellymann. I have a Synaptics Touchpad as well, and am familiar with, at least, my version of it. Here are some additional suggestions.
I understand that you are interested only in being able to change the sensitivity of each axis individually, however, having said that, I would still explore the following:
First, under the Sensitivity setting options, there is a setting for 'Palm Check' as well as a setting for the degree of "'Sensitivity.' Have you first tried the various different Palm Check levels and then
reset your 'Sensitivity' level?
Second, there is a 'Reset Devices' button on the Mouse Properties screen. Have you tried that, and then re-set all of your options/preferences (including Palm Check)?
Third, have you checked with Synaptics to make sure you have the most recent driver
for this device, and that the driver was installed without any corruption?
Fourth, are you sure this is not a hardware problem with the touchpad itself? Perhaps you need a touchpad repair or replacement