What's not immediately obvious is that Common Cause assigns the quests available that day. The questgiver in each locale alternates between the two short zone quests. If you take Common Cause, but wait until the next day to complete it, the questgiver will not offer the zone quest you need, and you'll have to wait yet…
I'm curious as to what privacy laws restrict you from talking about bans for an online videogame. Drizzt@drows4lyfe isn't PII, and I really can't think of anything else even in the ballpark.