hi ya there mate,can you obtain a usb mouse from somewhere,,,maybe a friend,or a shop...no more then a fiver £5 birtish money......give that a try....it may be your ps/2 slot but i would like to be able to rule that out with the usb mouse.........
see the thing is rollerball mice, have a tendancy to break qiute easily..the ball runs along 4 spinldes that have a round pice of plastic on them,,,,the round piece of plastice controls the axis obviously up down left n right,,,these can become kapupt quite easily.
try usb then let me know....
could be hardware issue yet,
regards
danzil