I had this problem after replacing the starter rope, and it drove me nuts for a day before I figured it out. If you take the metal tube off, you will see the plastic cable guide. It needs to be pushed into the metal shaft as far as it will go. Use needle nose pliers to grab one of the plastic flanges and push until it bottoms out. Then you can slowly turn the cable until it drops into engagement with the spool head. Button everything back up and you should be good to go. Of course, make sure the cable itself isn't broken first.
CarlD, February 2008