Reported: The "Accept quest 1[Main]Beginner" window keeps opening whenever a new quest is taken, even though Beginner is finished.
Found: The server never sent the game the list of quests you have completed. That list is how the game knows a quest is done, so it kept offering Beginner as one you could still take.
Fix: In the next DragonSoul update the server sends your completed quests at login, so the game stops offering quests you have already finished.