I just fixed mine, and it's easy. You'll need a set of pliers, a small phillips head screwdriver with a long shaft and a flathead screwdriver. First, order a replacement clutch from several online retailers -- do a search for "cuisinart clutch" -- they run about 8 bucks. After you have the part, you'll need to remove the three screws from the bottom of the blender. Leave the motor in place. Turn the motor assembly over, and you'll see a small insert on the bottom of the rotating shaft that accepts a flathead screwdriver. Have someone hold the metal piece in place (where the broken plastic clutch once was) with the pliers, and then turn your screwdriver CLOCKWISE (not counter-clockwise, as one would normally do). The metal part should unscrew. You might want to use a bench vice or a pair of vice grips instead. It took me five minutes to get the old part off. Then just screw the new piece on after putting the base back together -- screw COUNTERCLOCKWISE when putting it back on.
Good luck! It's really easy! I promise!
Dave Kaplan, January 2008