Okay, problem solved. I used a different e-mail address for my Cleverbridge purchase, and because this didn't match the e-mail address I use for my answers account, the activation process refused to recognise my input (despite the fact I used the correct e-mail address in my activation details!). This isn't a great detail, guys. If you want people to enter their answers e-mail address right at the start of the activation process (rather than at the user details stage), this should be made clear. Many business users - like myself - use multiple e-mail addresses. Anyway, I'm looking forward to exploring the new software!