A couple of ideas for you:
Put a large pair of pliers on the old chuck and see if there is any way that you can get it open to get the bit out.
If that doesn't work then the best thing to do would be to get a Dremel Tool with a bit that cuts into metal (metal cutting bit) and try cutting down the side of the chuck. Then you can also try splitting it open with a chisel.
Don- www.toolsandmachinery.com, March 2009