what was installed "synaptics.i386" or "xorg-x11-drv-synaptics"
yum install synaptics
Package synaptics is obsoleted by xorg-x11-drv-synaptics, trying to install xorg-x11-drv-synaptics-0.15.1-3.fc9.i386 instead
Package xorg-x11-drv-synaptics-0.15.1-3.fc9.i386 already installed and latest version
try removing synaptics.i386 and reinstall "xorg-x11-drv-synaptics" and reinstall the 3d driver ( nvidia or ati) .Using the install dvd in rescue