Read my sail hoist FAQ:
http://www.hobiecat.com/community/viewtopic.php?t=371
Aside from possible issues with the track itself... it is quite common to have the sail bind as it reaches this point in the mast, Comp Tip or not. It has to do with the luff curve sewn into the sail shape and the straight mast track. If you simply yank on the halyard without properly feeding at the bottom... it will bind as the halyard tension causes the luff to curve and bind in the track. Less halyard tension and more feeding at the track opening is typically the trick. You have to force the sail up the track... not simply guide it into the opening.