I have had Excel 2007 for a little over a year.  A few weeks ago, I noticed
that when I double-clicked on an Excel spreadsheet from within Windows
Explorer, Excel opened but the workbook did not.  Neither did the "Book1"
workbook.  It looked just as Excel would look if you opened it and then
exited the workbook, leaving the application open.

If Excel is opened in this manner and then I double-click a second time on
the workbook, then it opens.

I do not think that this is related to SP1, but SP1 was automatically
installed on 4/11/08.  I cannot recall if this problem cropped up before
that date, but I think that it did and it does seem unlikely that a service
pack update would cause such an obvious error.

Does anybody have any ideas as to what could cause such a problem?
Thanks in advance.

Alan