Blizzard has released a hotfix update to deal with a number of bugs and to tweak some classes. We can’t post the patch notes here because it contains spoilers and we don't want people to get mad at us, but the gist of the update is that it tweaks one problematic event, adds an error message when you try to remove a gem from an item with no sockets (rather than disconnecting you from Battle.net), adds fix to being attacked while resurrecting a team member (it will now interrupt the process), adds another fix to the dual-wielding of two-handed weapons bug, and adds several tweaks to the Monk, Wizard, and Demon Hunter classes. The patch notes can be found here.
On a related note, Blizzard has said that it has found no evidence that accounts are being hacked and that whatever is causing some accounts to lose characters, gold, and items is only affecting a small handful of players. If the problem is not related to being hacked then one would have to assume that it is some sort of odd bug. Blizzard is still looking into it, whatever it is.