I am running Office 2007, on Windows XP Service Pack 3, brand-new Dell Latitude E6500.
Excel was crashing without fail whenever I tried to close a document with using the close box (top right). I mean Close Window, to close the document, not the one to close Excel itself. It didn't crash when I closed my doc using the Close menu item in the Office Button.
I seem to have resolved it by disabling the COM Add-in "Send to Bluetooth":c:\windows\system32\btsendto_office.dll