Thanks for talking the time to post this fix, I've been trying to figure out why this started happening in our environment for the past week. Was just about to give up and call Microsoft when I saw this post, removed a few unused accounts and bingo! it's working again.
If the guy sends you the blog I'd be interested to read it as I'm curious why this would cause that error. Only thing I can think is that it's causing issues when it submits request for the site control file, if that contains the list of accounts it could be causing the root key to get truncated of the end but seems odd that it would only impact media creation.