[rhonda.feldbauer@bossoft.com]

Can you try this:
    Activate "Open", True

    SmartDialog("Open", "File name:<Editable text>").Value = "c:myfile.txt"

    SmartDialog("Open", "Open<Push button>#focusable#").Click

It is case sensitive and watch your spacing…
Or this:
    Activate "Open", True

    SmartDialog("Open", "File name:<Editable text>").Value = "c:myfile.txt"

    SmartDialog("Open", "Open<Push button>#focusable#").doAction