When a new user registers, their account is not activated until they click on a confirmation link sent to their e-mail address.
However, if they do _not_ put anything in the Location field of the registration form, they do _not_ recieve a confirmation e-mail.
So, if you never got the e-mail message, there is no link to click on and your account remains inactive.
It took me three failed registration tries before I compared new users that had failed to register to users that had succeded (and were posting messages) to notice that the successful ones all had entered a location.