I've noticed this bug in the 1.1 version, it seems to happen to me if I get the quest items before the quest. Most common happening with this, and easiest to reproduce is with the bard missions to collect the flute, lute, or drum.
I have heard of the bard's college as well, and i had the quest item post getting the quest, and can not drop it...its annoying I wonder if there is a way to give it to someone like angeir or if you are supposed to??
cause you are technically supposed to speak with delvin to complete the "special assignments" but the quest is already complete in your quest log..