Sorry to tell you this, but if the wires are ok then the fault is in the unit and will need replacing. Check that the ignition switch is working ok, a simple continuity test will tell you this. Remove the starter cover and trace the wire to the ignition unit from the switch, with the engine stopped take a new peice of wire from the ignition unit terminal to ground, remove the spark plug and test for a spark, if it still sparks then you definetly require a new unit. As this is a saftey issue it needs to be sorted out before useing the saw again
Husqvarna man, October 2009