click the "Reply to. . ." rather than the "Create. . ." button.
Something similar happened to me.
She was on a school board in New york and response email was getting sent to me. After contacting her we determined it was a simple problem. Case letters.
How often have you tried to set up a new account somewhere to have to keep retrying to come up with a user name not already used? This could very likely be the problem.
I would none the less change passwords every so often just to be sure. As an added measure to keep my contacts list from being "hijacked" I've added Aa@A.net, a bogus name at a bogus isp.
Depending on your provider special characters (#&~!^etc) may be used in your password. To the best of my knowledge programs used to hack passwords do not use these characters.