Sounds like you have the wrong field on your layout.
Set up your "associated user" field with your drop down menu instead of placeing a copy of the name field from the Personnel table on your layout and this should no longer happen.
Next step would be to stop using the name field for this relationship. Use a PersonnelID number (set it up as an auto-entered serial number) and link it to a matching number field in your assets table.
That way, when Mary Smith gets married and changes her name to Mary Jones, you can alter her name in the Personnel table and not have all her related Assets records disappear. :smileywink: