runtime error 2448: you can't assign a value to this object. access

Question

I have an access database used by multi users. The users are using two different names of drives (mapped networks like k and R) the users who using k drive have received an error "runtime error 2448: you can't assign a value to this object" This error is received by very rarely and disappeared on the next day. The time being the users are few times logged out and logged in to the database to solve the problem. Version info: Access 2003 and Windows XP Professional.
I don't know why it is happened and how to solve the problem. The problem is appeared in one the form tab when clicking the button.
Please see the following code.

---------------------------------------------------------------
Private Sub cmdDoClientSlip_Click()
  Dim strReportName As String
  Dim strRecordSource As String
  Dim blnDoFax As Boolean
  Dim blnPrintExtension As Boolean
  Dim vSelectedExtnID As Variant
  Dim strErrMsg As String
  Dim tbTextboxTime As access.TextBox
  Dim tbTextboxCount As access.TextBox
 
  blnPrintExtension = Me.chkPrintExtension.value
  blnDoFax = Me.chkApp_Confirm_DoFax.value
 
  strReportName = "rptClientConfirmationWithSig"
  strRecordSource = IIf(blnPrintExtension, "_qrptClientConfirmationExtension", "_qrptClientConfirmation")
  If blnPrintExtension Then
    vSelectedExtnID = Me.txtSelectedExtensionID.value
  Else
    vSelectedExtnID = Null
  End If
  strErrMsg = "Cannot " & IIf(blnDoFax, "fax", "print") & " Client Confirmation Slip"
  Set tbTextboxTime = Me.App_Confirm_Time_Printed_Client
  Set tbTextboxCount = Me.App_Confirm_Count_Printed_Client

  Call printfax_confirmation_slip( _
      p_strReportName:=strReportName _
    , p_strRecordSource:=strRecordSource _
    , p_blnDoFax:=blnDoFax _
    , p_blnPrintExtension:=blnPrintExtension _
    , p_vSelectedExtnID:=vSelectedExtnID _
    , p_strErrMsg:=strErrMsg _
    , p_tbTextboxTime:=tbTextboxTime _
    , p_tbTextboxCount:=tbTextboxCount _
    )
 
End Sub
-------------------------------------------------------------------
Private Sub printfax_confirmation_slip( _
                                      p_strReportName As String _
                                    , p_strRecordSource As String _
                                    , p_blnDoFax As Boolean _
                                    , p_blnPrintExtension As Boolean _
                                    , p_vSelectedExtnID As Variant _
                                    , p_strErrMsg As String _
                                    , Optional p_tbTextboxTime As access.TextBox = Nothing _
                                    , Optional p_tbTextboxCount As access.TextBox = Nothing _
                                    )
'--
'-- sanity check: the current record must be an Approved Application
    Dim msg As String
    Dim strAction As String
    Dim errNum As Long
    Dim errDesc As String
   
inits:
    strAction = VBA.IIf(p_blnDoFax, "fax", "print")
   
    Select Case True
      Case Me.App_EnqOnly.value = True
          msg = "ERROR: cannot " & strAction & " an ENQUIRY"
      Case Me.App_Outcome_Status <> "A"
          msg = "ERROR: can ONLY " & strAction & " an APPROVED application"
      Case Else
          msg = ""
    End Select
   
    If msg <> "" Then
        Call VBA.MsgBox(msg, vbOKOnly, p_strErrMsg)
        GoTo cleanup
    End If
   
    '-- must open application in EDIT mode, since we must pass this print/fax directive
    '-- to the Report via the database table
    If Me.App_Confirm_DoFax.value <> p_blnDoFax Then
        Me.App_Confirm_DoFax.value = p_blnDoFax
    End If
   
    '-- keep count of #times printed
    If p_tbTextboxCount Is Nothing Then
        '-- don't keep stats
    Else
        p_tbTextboxCount.value = p_tbTextboxCount.value + 1
    End If
   
    If p_tbTextboxTime Is Nothing Then
        '-- don't keep stats
    Else
        p_tbTextboxTime.value = VBA.Now()
    End If
   
    '-- save current record first
    If Me.Dirty = True Then Call cmdSaveRecord_Click
   
work:
On Error GoTo handle
   
    Dim strWhere As String
    Dim rpt As Report
    Dim strArgs As String
   
    If p_blnPrintExtension = True Then
        '-- print a similar report bound to a different datasource
        If VBA.IsNull(p_vSelectedExtnID) = True Then
            msg = "ERROR: must select an EXTENSION before printing it"
            Call VBA.MsgBox(msg, vbOKOnly, "Print/Fax Confirmation Slip")
            GoTo cleanup
        Else
            strWhere = "[Extn_ID] = " & p_vSelectedExtnID
        End If
    Else
        '-- NOTE: App_ID here is a CONTROL name on the report, not table field name!
        strWhere = "[App_ID] = " & Me.txtApp_ID.value
    End If
   
    If Len(p_strRecordSource) > 0 Then
      strArgs = p_strRecordSource & ";" & strWhere
      Call Application.DoCmd.OpenReport( _
                ReportName:=p_strReportName _
              , View:=acViewPreview _
              , OpenArgs:=strArgs _
              )
    Else
      Call Application.DoCmd.OpenReport( _
                ReportName:=p_strReportName _
              , View:=acViewPreview _
              , Wherecondition:=strWhere _
              )
    End If
   
cleanup:
    Exit Sub

handle:
    MsgBox err.Description
    Resume cleanup
End Sub

Thanks for your help