Looks like a bug to me!
Obviously, the simple WScript.Echo is paying attention to the Locale and is giving you the DD/MM/YYYY format you expect.
But for some reason INPUTBOX is ignoring the locale.
What you *MIGHT* try is converting the date to string *before* passing it to the inputbox.
Humor me and try this:
today = CStr(Date())
strValue = InputBox("Enter Start Date:","Test", today)
It may be wrong--it might always show MM/DD/YYYY--but at least it should be consistent.