Really strange problem…
My Toshiba A100, xorg, ubuntu packaged. In KDM the touchpad works just great, then you login into KDE and at some point during the splashscreening the pointer freezes. You can get the pointer moving again by rmmod/modprobe psmouse, but it gives you a normal mouse, no taps no scrolls. At the end of digging around here is the xorg.conf that works (relevant parts):
Section "ServerLayout" Identifier "Default Layout" Screen 0 "aticonfig-Screen[0]" 0 0 InputDevice "Generic Keyboard" InputDevice "Configured Mouse" "CorePointer" InputDevice "TouchPad" "AlwaysCore" EndSection Section "InputDevice" Driver "synaptics" Identifier "TouchPad" Option "Device" "/dev/psaux" Option "Protocol" "auto-dev" Option "LeftEdge" "1700" Option "RightEdge" "5300" Option "TopEdge" "1700" Option "BottomEdge" "4200" Option "FingerLow" "25" Option "FingerHigh" "30" Option "MaxTapTime" "180" Option "MaxTapMove" "220" Option "VertScrollDelta" "100" Option "MinSpeed" "0.09" Option "MaxSpeed" "0.18" Option "AccelFactor" "0.0015" Option "SHMConfig" "on" Option "SendCoreEvents" "true" EndSection Section "InputDevice" Identifier "Configured Mouse" Driver "mouse" Option "CorePointer" Option "Device" "/dev/input/mice" Option "Protocol" "ExplorerPS/2" Option "ZAxisMapping" "4 5" Option "Emulate3Buttons" "true" EndSection