Workbook.Save makes Userform Disappear

Hi,

I have a problem with saving a workbook from a userform. Saving takes about 5 seconds and therefore I change the Save-button color until the saving process has finished. On my computer everything works fine. On the users computer the userform disappears and a worksheet gets visible. Clicking on the taskbar and then on the worksheet brings the userform back. We both run Office 2013 on Windows 7 and we both use the same path for the program.

Private Sub Menu1SaveButton_MouseDown(ByVal Button As Integer, ByVal Shift As Integer, ByVal X As Single, ByVal Y As Single)

    Menu1SaveButton.BackColor = &H8080&
    Menu1SaveButton.Caption = "Saving..."

End Sub


Private Sub Menu1SaveButton_Click()
                 
    ThisWorkbook.Save
    
    Menu1SaveButton.BackColor = &H80FF&
    Menu1SaveButton.Caption = "Save"
       
End Sub

How can it happen that this simple code works fine for me but not for my user? I want to avoid showing worksheets at all times. Any help very much appreciated.

Just to update this thread: The problem was/is an unstable office installation. The user changed his computer and now saving application works fine.