A family of Microsoft word processing software products for creating web, email, and print documents.
I had this problem after installing the Excel PowerPivot add-in with Excel 2010. It seems to be resolved simply by disabling the PwerPivot COM Add-In.
You then have to re-enable PowerPivot when you want to use it, but I guess you are unlikely to be using PowerPivot in an embedded spreadsheet, so it's a workaround!
Andrew Hudson