Hi Neil,
Thanks for taking the time to write in. Generally in this situation the user has more than one account, this used to happen a lot back before 2011. Then we changed our login process.
1. If you logged in with email, you should use the userid instead.
If that isn't it, then the next question is
2. whether you used a different email when you joined and paid.
Let us know, thanks.
bidslammer