Contacts list error

Contact List errors! This is info for programmers!
I entered an e-mail address into the “Contacts” list. I discovered that the address was incorrect. I edited the contact entry. New entry showed the correct address. I tried to send to this corrected entry. The “auto complete” for the “To” line showed both the old entry AND the new entry. I deleted the entry and “auto complete” still showed both entries. I closed “EM Client”. I restarted "EM Client and. “auto complete” still showed both address listings (there is NO such address in the “Contacts” list at all at this time). I restarted Win-7 Pro. “auto complete” still brings up BOTH addresses. The “Contacts” list seems to have many problems. I only remember having problems with the “Contacts” lis but can’t remember details. I just figured out what to do and kept working.

unfortunately I was not able to replicate the issue, what mail service are you using?
Is it possible the contact was synced with the online mail service.