Account problems

I have a very weird problem with my account. I’m logged in at one computer, but I can’t log into it from another computer. Maybe I don’t remember the password correctly.

But here’s the strangest part: when I try to reset the account’s password, if I type in my nickname “Malcolm”, nothing arrives to my mail, and if I type in my email, it says that I’m not registered even though I get summary emails from this website. However, when I try to register, it says that “Malcolm” is already taken. What’s going on and how can I rectify this?