There’s never any excuse for a NullReferenceException, and Microsoft themselves should know better. This was thrown when I tried to launch Live Writer before unlocking a drive on my laptop secured with BitLocker (i.e. it was unavailable). Honestly, how lazy do you have to be not to trap that and pop up an intelligent message?
I’ve seen a lot of things like this lately (well, since turning on BitLocker) - software that depends on the file system but that doesn’t bother to check whether it’s available. Attention to detail, anyone?