Before jumping the gun, could at least one of the logitech owners try using something like intellipoint drivers or just no drivers at all (if that works for G5 at least)
i have a G5 and G7 i DID have those stupid drivers installed and then said fuk it removed all mouse drivers and used the vinilla xp drivers...problem went away for me.( and i can still adjust the sensitity on the fly as well)