After having a different password/same email mix-up with Mturk/Amazon Payments, I moved the account I've been using to a different email and decided to open up an account on the email I've been using. I looked up in the rules to see if having two accounts was against the rules and I could not find anything against it. I sent Amazon an email before I did any hits just to make sure. I was doing great on mturk too, I only had one rejection! The other account doesn't appear to be banned yet, but I don't want to take any chances. Amazon doesn't appear to be answering my emails right now. I wasn't trying to scam. I looked at the rules and couldn't find anything!
Terms of Service Section 3 subsection b: b. Providers in General. You may only register once with Mechanical Turk as a Provider Good luck, hopefully they will help you sort it out. Amazon is very frustrating to communicate with.