Actually, I have the same problem and I've been struggling with it for a day now. It was working fine when I went to bed, it DID NOT get touched overnight, and in the morning, error 208.
However, something installed a bluetooth driver over that same night, without my permission, and everything's been screwed since that.
I've tried deleting everything and reinstalling but now the SteamVR installation fails.
Please tell me there's a fix for this other than reinstalling Winblows.