This is a brand new installation of trial Office 2007. I tried to open an
existing Excel 2003 files as usual by double clicking on the file name. Some
of them open, but some of them don't. All I see is the ribbon and solid blue
screen below. Then I click on File-Open and it opens.

What's the problem with those Excel 2003 files? Why some of 2003 open by
doubleclick by the other ones only manaully by File-Open?