the magical reappearing form

Hi guys! I have a problem involving 3 forms - a principal form (frmPrincipal), a form used to filter records(frmFilter), and a third form used to perform operations on the filtered data (frmContacts).

In frmFilter, I have the following code which I use to change the image on a button from a traffic light with the light red to a traffic light with the light green. This is so that the user is distracted while the records are being filtered.

Code:

---

cmdContinuar.Picture = Image1.Picture

HourInitial = Time
HourFinal = Time
Do While HourInitial = HourFinal
    HourFinal = Time
    DoEvents
Loop
HourInitial = Time
HourFinal = Time
Do While HourInitial = HourFinal
    HourFinal = Time
    DoEvents
Loop

Me.MousePointer = vbDefault
DoEvents

Me.Hide

With frmContacts
    If frmPrincipal.UseGroups = True Then
        .lblGroup.Caption = "Group:"
       
    Else
        .lblGroup.Caption = "Level:"
       
    End If
   
    .lblLevel.Caption = txtLevel.Text
    .lblPeriod.Caption = cmbPeriod.Text
    .Show vbModal, frmPrincipal

End With

Unload Me

---

On occasion, when the user enters the filter criteria, proceeds to frmContacts, and then closes frmContacts, the same form will pop open again. It only happens about 10% of the time, which leads me to believe that it has something to do with the above loops and DoEvents statements.

Why is this happening?

Thanks,

Andrew