This is driving me mad.

I have a series of Macro's which, thanks to some help from this forum, were working perfectly.

An example: 
Sub Workbook_OB()
    'Forms ToolBox
    Dim i As Long
    Dim cnt As Long
    cnt = 0
    With Sheet1
        For i = 130 To 134
           If .CheckBoxes("Check box " & i).Value = 1 Then
                cnt = 1
                Exit For
            End If
        Next
    End With
    If cnt = 0 Then
        MsgBox "Please choose an option for the Sentencing Occasion"
        Exit Sub
    End If
    cnt = 0
    With Sheet1
        For i = 137 To 141
           If .CheckBoxes("Check box " & i).Value = 1 Then
                cnt = 1
                Exit For
            End If
        Next
    End With
    If cnt = 0 Then
        MsgBox "Please choose an option for the Custodial Occasion"
        Exit Sub
    End If
End Sub
The Macro checks that at least one check-box in a range has been ticked, and returns an error if that is not the case.
However. If I attempt to replicate this Macro but for a different range of check-boxes, by copying the code into a new module and changing the numbers, I.e 
For i = 137 To 141
To

For i = 601 To 642
I suddenly am getting an error message(s):

Unable to get the value property of the checkbox class.
OR
method checkboxes of object _worksheet failed

What has changed!?

I have a feeling there is something going on around where my macro's are saved and stored. But it doesn't work even if the module is hosted in my Personal.xls file.

I would really appreciate it if somebody could shed light on this for me. This place is becoming like my second home...