Update record via combobox selection in subform

[Rosie]

I have a main form with header info w/ 'tHeader' as the control source.

I have a subform with 'tDetail' as a control source.

They're strung together by a field named MA_ID.

This works fine.

I have a field within the subform that I want to update via a combobox located on the same subform.

The field I want to update is currentissue. It's a field on the tDetail table.

There is another field on the tDetail table called SubIssueReason.

Based on the selection chosen in currentissue, I want to display certain possibilities in the SubIssueReason combobox. I have done this and it works fine. Here's how I'm establishing rowsource in the combobox:

Private Sub CurrentIssue_AfterUpdate()
Dim strSQL As String


If Not IsNull(Me.CurrentIssue) Then
        Me.IssueSubReason = ""
        strSQL = "SELECT qissuesubreason.issuesubreason " _
        & "FROM qissuesubreason " _
        & "WHERE  " _
        & "qissuesubreason.issuecode='" & Me.CurrentIssue & "' " _
        & "ORDER BY qissuesubreason.issuesubreason"
        Debug.Print strSQL
        MsgBox strSQL
        Me.IssueSubReason.RowSource = strSQL
End If

End Sub

So: the combobox populates appropriately, but I am unable to select anything in it--I arrow down, the appropriate options appear, but I can't select them.

I understand this question has been asked and answered about a thousand times and this is not the freshest of problems, but I can't figure out why this thing isn't working for me, and I've been on it for three days. So I humbly beg your indulgence. I have read Rabbit's overview from 07 on this and have been unable to figure out where I'm going wrong.

[Rosie]

Sorry, I meant to add:

Based on the overview I read, the row and control sources seem right--the rowsource is set via the code above, the controlsource is the tDetail table.