With the release of Hearthfire one of Skyrim's quest, Waking Nightmare, seems to be bugged for quite a few people. It's the quest in Dawnstar (I believe) that is needed in order to purchase the property to build one of your houses on. The quest seems fine until you get to the part where you have to drink the Torpor Potion. From this point on saving or bringing up a menu that auto-saves will cause the system to freeze. To fix this don't pull up any menu's or attempt to save until the quest is finished and you are out of the temple (worked for me at least).
Subject: Skyrim Bug: Hearthfire