Before the patch: I had solved the mushroom spore quest but the cure remains in my inventory and the quest remains uncompleted in the diary... if I try to discard the potion the quest comes back. I've checked the forest and the imps are definately gone (cured one presumes).
If you solve the quest, you do get a temporary quest solved message ( "I've freed the paralyzed imps and as I expected, they were very grateful.")
However as soon as you try to move the potion the quest reappears in your log.
