This quest is given by Svari to eventually recover Roggvir's

However, when I'm going into the catacombs, the

has the "steal" mark.

Well, Bethesda, "http://www.youtube.com/watch?v=0srO4LTzVTE".

I haven't "stolen" it, because my character isn't a thief. Is there someone who has/had the same problem? Do you have any advice?

As far as I can recall, it never had the steal option before.

Are you on PC? If so you can console...

clearownership

...on it.

Nope, I'm on the X-Box. Sorry, should've listed that in the OP. Good to know, though. I'm planning on getting the PC version soon. Thank for that command. It'll proof useful soon.

Sorry, but I have no idea how to help with the console version of the game. One thing to note though is that if you ever want to do that quest on another character you can loot his body for the amulet right after he gets executed. It'll start the quest for you and you can simply walk up to Greta and you'll be able to give her the amulet.

Yes, that's what I did on every playthrough. I heard it could cause quite some bugs if you're having more then one amulet, though.

Guess my best option would be doing random stuff, waiting for a while, and see if the issue remedies itself. Assuming it's a bug.

I haven't done that quest the 'regular' way for a very long time so I don't recall, but is it clear that the amulet shouldn't be marked as "Steal". Just like the Riften skooma dealer quest when you get the note out of the satchel it's always marked "Steal", but it makes no difference and I don't know that it counts against your character.