take spindle out and try put in a wide flat head screwdriver i see this all the time
normally the lock part which grabs the spindle has worn out or broke have you tried turning the key all the way open to release the lock without using the handle. if its a front door which does not open on outside with handle but does on inside usin a split spindle it might not be in lock properley as it does not pass all the way through
mark sneyd
June 2009