User blog comment:Neguy71inok/Glitched in Riften/@comment-4640959-20111215195143

If you went to Honeyside first before you talked to the Jarl, there is a (unconfirmed) bug that Becoming Thane won't be possible in Riften. If you can, you should reload and talk to the Jarl about becoming Thane before visiting Honeyside or buying decor.