strange behaviour: deleting user from Membership

[Rich]

When I delete a user from membership, it does not get deleted but
disabled.
So, when I add a new user with same spelling but different case, it
instead adds the old user.

eg:


Membership.DeleteUser("Louis", true);// Capital "L" here

Membership.CreateUser("louis", "password","email");// Lower-case "l"
here

Instead of adding user "louis", it added the old user "Louis".

According to msdn2, this should have not happened.

Is there a workaround this issue?

Thanks,
Rich