I was updating an invoice in the Customer Center. Fat-fingered something and deleted a line of my invoice.  I cancelled what I was doing, intending to reopen the invoice to make the correction.  But the customer was gone from my list.  I searched for the customer name and an entirely new, blank customer center list opened, with just that one customer.  When I take the customer's name out of the search box, the rest of the list reappears.  I cannot see anything different in the setup of the customers.  Any ideas why this is happening?