Delete Employee or User problem

[ctk]

Hi,
I have initially created an employee. Then using this employee record, I create the user account. It works fine. But when I go to (for example) "Activites" section, and try to do an advance search, in the "Assigned to" list box, I have 2 entries of my user that I have recently created. Then I delete both user account, and recreate a new account with the same user name, it works, but in the same list box of the advanced search, I have now 3 entry of the same user name.

Any ideas? Thank you in advance.

CTK