Creating New Customer

I have a customer that is trying to creat and account to login into servicecamp but keeps getting an error that the email address already exists.  I have only two customer accounts and neither one is using the address of this customer.  I did try to create the account manually which worked but the customer could not use that account because no password was set.  I deleted that account and tried to get the customer to create the account again but their are still getting the email account already exists dispite the account being deleted.  Don't understand why the customer is getting that error or how to fix it.