Ok well with recent investigation of the newer W/P AWOD models, we have found that too much detergent can cause this problem (too many suds going where they shoudnt). The appliances we have seen are very new, sometimes first time use. If the appliance you have is a AWOD model then this could well be the problem.
Generally the service light just comes on because the appliance is timing out somewhere (normally drain) but is functioning properly.