User blog comment:Darker-than-night/Odd bug./@comment-1992639-20120428140221

It seems to occur when the game somehow can't revert you back to your race whenever switching races. When you change into a werewolf, the game changes whatever race you are temporarily into the werewolf race. Likely, the game screwed up and not knowing what to do turned you into the default race, the Nord. Nord bodies, when the game tries to fit on a non-Nord head, become headless.

Were you a Vampire Argonian by any chance? The game treats those as an entirely unique race also, not as just Argonians. It may have bugged up there.