Login IDs are shared across the server that your database is on.  This means that each organization's database on that server has to have unique Login IDs.  If you receive the error message "You have entered a login ID for the account which has already been reserved by another eTapestry user", this means that another organization is using that Login ID.  You will need to create a more unique login ID (example: adding numbers) and the system will allow you to save the new account once it verifies that the Login ID is not currently in use.