From what I can gather:

It involves Level Turnins and some exploit. My best guess is there is some way via macros or 3rd party to cancel a quest turn in and turn it in at the same time. It's via spamming and it's normal thats for sure. The real question, is if the problem is related to all leve quests or just that particular one. And if that particular one, which one is it? Even the generic mmo hacker sites are stumped with this one.