DeLonghi Magnifica grinder won't stop!?

My DeLonghi Magnifica ESAM 04.110S stopped working when the grinder became clogged. Successfully dismantled, cleaned & re-assembled grinder but now when power switch at rear of machine turned on grinder runs continuously. No electrical work carried out other than disconnecting grinder leads & replacing them on re-assembly. Leads labelled to ensure they went back from where they came. Any ideas as to cause & solution for the problem?