Hi, These chucks are very common to fail, you will probably find, if you can get the arbour out, that the small flutes sticking out of the chuck body have snapped off or are worn. It is a new chuck I'm afraid. You will be able to pick one of these up at your local tool hire shop, or local tool repair shop, and will cost around £30. If you take off the front rubber of the chuck, you will see a circlip, take this off, and remove the washer below, you can then take the plastic cover off and remove the ball bearing holding the arbour end in place, you should be able to push this out with a small punch or screwdriver from the back of the chuck, with the bearing removed, but remember to check the 2 flutes sticking out, if they are snapped off or are worn (test with a good drill bit and check for ecessive play), replace the chuck, as this will damage any other bits you put into it, and get stuck in.
I hope this helps!!!!
Dave the tool repairer., June 2007