User blog comment:Misterfish/Annoying glitch (pre-patch)/@comment-1960986-20111206215932

Ahh something else... There is another problem within the quest that requires you capture a dragon. If you are attempting to do this quest without the Jarl and are attempting to capture the Troll Dragon, do not attack the dragon until you use 'dragonrend' on it. This is the only way to complete the quest on your own without the Jarls' help.