One has seen that under a few conditions such as regional settings and sadly one time we saw it with a Crack Windows copy. http://www.functionx.com/visualbasic/topics/datetime.htm covers regional settings.
I have generated dates for the first fourteen days of August to demonstrate the error. The dates are created using DateSerial function varying the day part; these are loaded into a combobox (and displayed via Msgbox to check); Msgbox displays the dates in dd/mm/yyyy format as expected but when the dates are displayed in the combobox they appear to be in mm/dd/yyyy format; selecting the first twelve entries I get the 8th of each month but selecting the last two entries I get the 13th or 14th of August! Needless to say, access to Microsoft has produced no one who can help as this is a coding problem or not to do with Office! I can supply demo code if required.