Hi James,
I'm away from my home computer right now, but once I get home I will go into your profile on our admin console and send your current login information to you - that should then let you see what email address you're using and change it if needed. If you need further help after that, do feel free to email me and we can work together to sort it out. I can't see that having used one address in the past should stop you from using it again now - the only way you'd be stopped from using it would be if you were currently using it for another account. For example, if you'd signed up under a second nickname (as some people have in order to post a story anonymously, for example) and used the yahoo address, then you can't use it as your primary address.
We'll find a solution - as I said, give me a couple of hours until I'm in a position to access the admin console.
Wendy