gzusrawx's problem isnt the same problem as the original poster here, i had the same problem, wasnt 8-10% everytime, it would be totally random when it stopped, sometimes it got to 100%.
in any case, every time no matter if the progress bar stuck at any % the unrar process would be successful. but altbinz would need restarting or else future par2 wouldnt be checked, repaired or unrar'd
what fixed it for me ive already explained, but must be something else causing it in this case