MS Access app shows "Enter parameter value" only on some machines

Question

In an MS Access app I have a main form that has some buttons, one of which is a "Calendar" button.

When this button is clicked, a form that implements some kind of calendar should open.

The problem is that on some clean machines where I deployed this, instead of the calendar opening, an Enter parameter value dialog opens. On 3 other older instances it works without this problem.

On that form there is an unbound control that has default value =Now()

Office version 2013.

Where and how can I look for differences between these machines?

I can add code snippets or print screens to this question if you let me know what part exactly.

UPDATE:

The code in the open form altough before this get's executed the "Enter parameter value" dialog shows.

Private Sub Form_Open(Cancel As Integer)

Dim PrstAnz As Integer

On Error GoTo Form_Open_EH

If DCount("[prst]", "FLMT_AKTPRST") > 1 Then
    'Es stehen mehrere Prüfstände zur Auswahl
    Me.prst.Visible = True
    Me.prst.RowSource = "FLMT_AKTPRST"
End If

Me![prst] = DLookup("[prst]", "FLMT_AKTPRST")

Me![ABeginn] = Date
InitPrst Me![ABeginn]

Exit Sub

All machines are Windows 7 x64 with Office 2013.

Answer 1

It's was about OS culture settings.