DVDfab to xvid, avi stops before movie ends?

Ive backed up two of my movies now to xvid and both have stoped before the movie ends… Nightmare on Elm street stops at 1 hour and 13 mins, DaVinci Code stops at 1 hour 26 mins… The xvids look and wound great but its lame when the file ends before the movie is over???

Am I doing something wrong?