The most common cause for that is that there is a video or audio fragment at the far end of your timeline. It may be so small you don't see it. Repeated clicking on the "next edit point button" may take you to that stray fragment.
I am having a similar problem, I did find one stray fragment, which I deleted. The video still seems to go on for another 13 minutes past where it should end. I'd be interested to know if you got your problem solved and how you did it. Thanks.