My guess is that the circlip that is located on the shaft alongside the spring is missing - probably broken. If the shaft (silver button on the side) that you press to release the top section of the mixer doesn't spring back when you release it then that will be the problem. You can buy the circlip for a few cents at any hardware store. You can see the groove in the shaft where the circlip fits.
wilsonsrus, December 2008
