advice on steam leaking from arm on Krups 963/B
 

We've had a small Krups capuccino/milk-steamer unit 963/B for
about 6 months, using it twice a day. Recently, it began to leak a
little steam from the frothing nozzle, no matter how tightly the
knob is turned shut. Is this a common problem, and is there any
way to stop it?
Thanks
Tim