Your problem is caused by the single apostrophe (') that is in the search criteria (Second O'Second 01/01/2000).
I do not use macros so I can not help with a solution for the correct syntax in your macro.
However, I do use VBA and I can offer a solution using that. Create an [event procedure] in the After Update event of the combo. Put the following line of code inside that procedure:
Code:
DoCmd.SearchForRecord , "", acFirst, "[Full Name] = """ & Screen.ActiveControl & """"
I have attached a copy of your front end for your perusal