Hotpoint WT761 door won't open?

I recently had a problem with the water pumping very slowly out of my washing machine. I've replaced the pump and now it pumps much better and faster. Unfortunately there is now a problem with the door. Once the washing cycle is complete, the door locked LED stays on and I can't open the door. I can only open it once the power has been switched off. It wasn't a problem before I replaced the pump.