Spreadsheet data delay on opening

When I try to open an existing Excel spreadsheet, the Excel program opens to a blank screen (no sheet, just a blue background). If I minimize or maximize this screen, the existing data appears. If I don't minimize or maximize, the data does not appear. If I open the Excel program itself using the shortcut icon, I can open an existing spreadsheet with no delay on the data appearance. What's up with that? (Adobe Reader 8 behaves in a similar fashion).
I am running Windows XP Pro, SP3 and MS Office 2007 with everything updated as of today.
Any help appreciated!