MS Access form combobox dropdown list does not refresh query for list

I have a form in MS Access 2003.  On the form I have a combobox dropdown.  
When the form moves to a new record, the query for the combobox list is automatically refreshed using a query that looks up the correct options for the ID of the record in the form.
 
Sometimes the combobox does not refresh the list and the choices remain the same as whatever record was first displayed in the form.  When I move to a new record in the form, the choices in the combo box never change.

I need to FORCE the combobox to reexecure the query to refresh the list in the combobox every time the form moves to a new record.  What is frustrating is that sometimes it works fine.  I can't figure out how to trace what is happening when it does not update the combobox list.

Combobox query:
SELECT tEventPackages.Package, tEventPackages.PackageLevel FROM tEventPackages
WHERE (((tEventPackages.EventID)=[Forms]![fEventParticipants]![EventIDx])) ORDER BY tEventPackages.PackageLevel;