Values of combo box in subform based on value in main form not working

[HLCruz via AccessMonster.com]

I have a subform on a main form in which I have been using the following
query under a combo box. This has been working very well but suddenly
stopped; interestingly there are a select few "RouteCodes" that work but
others which do not.

This is the SQL of the query under the combo box:

SELECT tblScheduledRoutes.RouteCode, tblScheduledRoutes.PickUpDate,
tblScheduledRoutes.ScheduleID, tblScheduledRoutes.Expiration
FROM tblScheduledRoutes
WHERE (((tblScheduledRoutes.RouteCode)=[Forms]![Form1]![Route]) AND (
(tblScheduledRoutes.Expiration)>Now()));


This is the SQL of the underlying query in my subform:
SELECT sysqryScheduledPickUpSubform.PickUpID, sysqryScheduledPickUpSubform.
ResidentID, sysqryScheduledPickUpSubform.RouteCode,
sysqryScheduledPickUpSubform.PickUpDate, sysqryScheduledPickUpSubform.
MissedPU, sysqryScheduledPickUpSubform.MailReceipt,
sysqryScheduledPickUpSubform.Instructions, sysqryScheduledPickUpSubform.Route,
sysqryScheduledPickUpSubform.CallerID, sysqryScheduledPickUpSubform.
Confirmation, sysqryScheduledPickUpSubform.ConfInst,
sysqryScheduledPickUpSubform.PickUpConfirmed, sysqryScheduledPickUpSubform.
ScheduledPickUp, sysqryScheduledPickUpSubform.MarkDelete,
sysqryScheduledPickUpSubform.UserCreated, sysqryScheduledPickUpSubform.
DeleteConf
FROM sysqryScheduledPickUpSubform;

This is the SQL of the underlying query in my main form:
SELECT tblResidentList.Address, tblResidentList.City, tblResidentList.State,
tblResidentList.Zip, tblResidentList.Route, [Address] & ", " & [Zip] AS Pkey,
tblResidentList.FName, tblResidentList.LName, tblResidentList.Phone,
tblResidentList.IntersectingStreet, tblResidentList.Email, tblResidentList.
HouseNumber, tblResidentList.StreetName, tblResidentList.DoNotMail,
tblResidentList.NoCalls, tblResidentList.SendEmails, tblResidentList.NoMail
FROM tblResidentList
ORDER BY tblResidentList.Address;

I'm not sure what else to post in order to help analyze my problem. Please
let me know if there's anything else I should include.

Thank you to anyone who will take a look at this!

Heather