I've been having trouble curing myself of lycanthropy. I have a witches head in my inventory, I've cured Vilkas and Farkas, and yet when I hit 'A' to interact with the Flame of the Harbinger, it does nothing. Any suggestions what I should try doing?

I had the same problem in my first playthrough. I don't know if you tried it already and if it's going to work (maybe I was just lucky), but after I had cured Farkas I still couldn't get it to activate, even with the heads in my inventory. So I went to Farkas at some point asking him for a random quest, and he gave me some bandit-clearing quest, and before visiting the bandit site and completing it, I went to the tomb first. At that point the Flame of the Harbinger activated, I tossed the head in, fought the wolf spirit and cured myself. At any other time it wouldn't activate, not even when I was on the quest to cure Farkas, but during the random quest it worked. In my second playthrough it worked when I cured Kodlak.

Alright, I'll have to give that a try.

I had the same problem in my playthrough and went back and tried again. It did not activate at first, but did so subsequently and I cured myself by defeating my wolf spirit. Trying again is the key.

I've tried it again several times, but haven't had luck.

as a last resort you might trying using the console to cure yourself of the disease. frankly there isnt much disadvantage outside of nothing getting 5-10 resting bonus.

I've got the 360 version, so I can't access the console. Will just have to deal with it, I guess.

Why would you want to? It's a gift!

Because I'd like to have the option of curing myself, at the very least? The Companions questline annoyed me because whomever thought it up decided to force players to become a werewolf in order to finish the questline. You'd think they would let you have the option of becoming a werewolf or staying normal and still let you finish the quest chain.